Printing apparatus, printing program, printing method, image processing apparatus, image processing program, image processing method, and recording medium having the program recorded thereon

ABSTRACT

An apparatus includes: a print head having nozzles which can print different sized dots; a unit acquiring image data having M-value density information (M≧3) per pixel; a unit acquiring information regarding density unevenness of the nozzles; a unit performing N-valued processing (M&gt;N≧2) on the acquired image to generate N-valued data; a unit generating print data from the generated N-valued data; and a unit that prints based on the generated print data, wherein the N-valued data generating unit determines generation ratios of the different sized dots for predetermined regions of the acquired image data based on the acquired density unevenness information, and performs N-valued processing (M&gt;N≧2) on the image data based on the determined generation ratios.

RELATED APPLICATIONS

This application claims priority to Japanese Patent Application Nos.2005-263441 filed Sep. 12, 2005 and 2006-171355 filed Jun. 21, 2006which are hereby expressly incorporated by reference herein in theirentirety.

BACKGROUND

1. Technical Field

The present invention relates to a printing apparatus, such as a printerof a facsimile machine, a copying machine, and OA equipment, a printingprogram, a printing method, an image processing apparatus, an imageprocessing program, an image processing method, a recording mediumhaving the program recorded thereon, etc., and particularly, theinvention is suitable for a so-called ink-jet type printing apparatuswhich discharges fine particles of liquid inks of a plurality or colorsonto a print sheet (printing medium) to draw predetermined charactersand predetermined images, a printing program, a printing method, animage processing apparatus, an image processing program, an imageprocessing method, and a recording medium having the program recordedthereon.

2. Related Art

Hereinafter, a printing apparatus, particularly a printer (hereinafterreferred to as “ink jet printer”) employing an ink jet system will bedescribed.

Since ink jet printers generally provide low-price and high-qualitycolor printed materials to be easily obtained, they have been widelyused not only in offices but also by general users along with thewidespread use of personal computers, digital cameras, and the like.

An ink jet printer is generally adapted such that predeterminedcharacters and predetermined images are printed on a printing medium andthereby a desired printed material is produced by discharging (ejecting)particles of liquid ink in the form of dots from nozzles of a print headwhile a movable body called a carriage integrally provided with acartridge and the print head reciprocates in a direction perpendicularto a sheet feed direction of the printing medium (sheet). Also, sincethe cartridge is provided with ink cartridges for four colors (black,yellow, magenta, and cyan) and a print head for each color, not onlymonochrome printing but also full color printing by combining therespective colors can be easily performed (furthermore, full colorprinting by combining six colors, seven colors, or eight colors in whichlight cyan, light magenta, etc. are added to the above four colors isalso put to practical use).

Further, in the ink jet printer of the type that is adapted to performprinting while the print head on the carriage is caused to reciprocatein a direction perpendicular to the sheet feed direction, it isnecessary to cause the print head to reciprocate from tens of times to100 times or more in order to finely print an entire sheet. Therefore,an ink jet printer has a drawback in that the printing time is longerthan printing apparatuses using other methods, for example, a laserprinter using electrophotography, such as a copying machine.

In contrast, in an ink jet printer of the type in which a long printhead having the same (or greater than) dimension as the width of a printsheet, and a carriage is not used, it is not necessary to move the printhead in the width direction of the print medium and printing by aso-called one scanning (one pass) is provided. Therefore, the samehigh-speed printing as a laser printer is provided. Further, since adrive system, etc. for moving the carriage which carries the print headbecomes unnecessary, this type of ink jet printer has an advantage inthat a printer housing can be made compact and lightweight, and noisereduction also improves significantly. The ink jet printer of the formertype is generally called a “multipass type” or a “serial” printer, andthe ink jet printer of the latter type is generally called a “line-headtype printer” ”

Since the print head of such an ink jet printer is configured such thatone row of or plurality of minute nozzles having a diameter of about 10to 70 μm are arranged in a printing direction at regular intervals, aso-called “flight deflection phenomena” may occur, including aphenomenon that the ink discharge direction of some of the nozzles maybe inclined due to manufacturing errors, a phenomenon that some nozzlesmay be disposed in positions which deviate from ideal positions, and aphenomenon that the landing position of a dot to be formed by thenozzles may deviate from a target point.

As a result, poor printing called a “banding (streak) phenomenon” may becaused in portions where printing is performed using the defectivenozzles, thereby noticeably deteriorating printing quality. That is, ifthe “flight deflection phenomenon” is caused, the distance between dotsdischarged by adjacent nozzles will become uneven. As a result, a “whitestreak” (in a case in which a print sheet is white) will be generated ina portion where the distance between adjacent dots is large, and a “darkstreak” will be generated in a portion where the distance betweenadjacent dots is short.

In particular, such a banding phenomenon tends to be caused morenoticeably in the “line-head type printer” in which a print head or aprinting medium is fixed one pass printing) than in the “multipass typeprinter” (serial printer) as mentioned above (in the multipass typeprinter, there is a technique that makes the banding inconspicuous bymaking the print head reciprocate several times).

Therefore, although research and development in hardware, includingimprovements in the manufacturing of a print head, improvements in thedesign thereof, etc. have been made in order to prevent poor printingcaused by such a “banding phenomenon,” it is difficult to provide aprint head in which the “banding phenomenon” is 100% eliminated from theviewpoint of manufacturing cost, technology, etc.

Thus, under the present circumstances, in addition to improvements inhardware as mentioned above, a technique to reduce such a “bandingphenomenon” using a so-called software technique, such as printingcontrol, is also used.

For example, JP-A-6-340094 entitled “Ink-jet Recording Apparatus andInk-jet Recording Method” suggests a method to reduce a “white streak”extending in a direction perpendicular to a nozzle arrangementdirection, which is caused by the “banding phenomenon,” by greatlychanging the size of dots in the a driving direction (perpendicular tothe nozzle arrangement direction) of a print head while the size of dotsin the nozzle arrangement direction of the print head are made the same.

On the other hand, although such a banding phenomenon is caused by theflight deflection phenomenon as mentioned above, it is known that thebanding phenomenon is also caused by the so-called “density unevenness.”

That is, this “density unevenness” is a phenomenon in which apredetermined size of dot is no longer printed because the printingposition is as normal, but the ink of each nozzle of the print head isnot discharged as normal, unlike the printing deviation caused by theflight deflection phenomenon as mentioned above. Accordingly, in a casein which ink is not discharged at all (non-discharge) and the inkdischarge amount is less than a specified value, no dot is printed ordots having a smaller size than a prescribed size are printed. Thereby,the density of only a line to be printed by the nozzle becomes low, andconsequently a “white streak” or density unevenness similar to the“white streak” is generated in the portion. In contrast, if the inkdischarge amount is excessively more than a specified value, dots havinga larger size than a prescribed size are printed, and the density of aline to be printed by the nozzle becomes high, and consequently a “darkstreak” or density unevenness similar to the “dark streak” is generatedin the portion.

Therefore, for example, in JP-A-1-129667 and JP-A-3-162977, thevariation with respect to the density data for every nozzle of a printhead is considered density variation so as be corrected. Specifically,JP-A-1-129667 and JP-A-3-162977 suggest a method of trying to reduce anydensity variation by correcting the pixel value (density value) of apixel of the image data corresponding to a nozzle whose ink dischargeamount is less than a specified value so that the pixel value may beincreased to a value greater than its original value, and in contrast,by correcting the pixel value (density value) of a pixel of the imagedata corresponding to a nozzle whose ink discharge amount is more than aspecified value so that the pixel value may be decreased to a valuesmaller than its original value.

Further, for example, JP-A-2002-19101, JP-A-2003-136702, andJP-A-2003-63043 suggest a method of trying to reduce the densityunevenness of a portion with dark density by using other colors for thecolor of the portion or increasing the ink discharge amount of a nozzleadjacent to a non-discharge nozzle with respect to a discharge failurephenomenon of a nozzle which does not discharge ink at all.

Meanwhile, in the above related art, with respect to the bandingphenomenon resulting from either the “flight deflection” or the “densityunevenness” caused by poor discharge, the effect of reducing the bandingphenomenon can be exhibited somewhat, but it cannot be said that theeffect is satisfactory. Further, it turned out that it is difficult tosatisfactorily cope with the banding phenomenon resulting from bothphenomena.

For example, although it is possible to reduce a “white streak”extending in a direction perpendicular to a nozzle arrangement directionby greatly changing the size of a dot as mentioned above with respect tothe banding phenomenon resulting from “flight deflection,” there is aproblem in that the density of the portion becomes high and “densityunevenness” is caused.

Meanwhile, although the method of using other colors for the color of aportion with dark density as mentioned above with respect to the bandingphenomenon resulting from the “density unevenness” caused by poordischarge, can reduce a color difference, it cannot be said that themethod is suitable for printing which requires high image qualitybecause a color tone may change. Further, although the method ofincreasing the ink discharge amount of a nozzle adjacent to anon-discharge nozzle is effective in a portion with thin density, theink discharge amount of the adjacent nozzle cannot be increased any morein a portion with dark density, but banding will still remain.

SUMMARY

Therefore, an advantage of the invention is that it provides a newprinting apparatus which can eliminate the banding phenomenon caused by,particularly, flight deflection or density unevenness, or can make thebanding phenomenon nearly inconspicuous, a printing program, a printingmethod an image processing apparatus, an image processing program, animage processing method, and a recording medium having the programrecorded thereon.

Aspect 1:

According to Aspect 1 of the invention, there is provided a printingapparatus including: a print head in which a plurality of nozzles whichcan print different sizes of dots are arranged; an image data acquiringunit which acquires image data having the M-value density information(M≧3) for every pixel; a density unevenness information acquiring unitwhich acquires information on the density unevenness of the nozzles ofthe print head; an N-valued data generating unit which performs N-valuedprocessing (M>N≧2) on the image data acquired by the image dataacquiring unit to generate N-valued data; a print data generating unitwhich generates print data from the N-valued data generated by theN-valued data generating unit; and a printing unit which performsprinting using the print head based on the print data generated by theprint data generating unit. The N-valued data generating unit determinesthe generation ratios of the different sizes of dots for everypredetermined region of the image data acquired by the image dataacquiring unit based on the density unevenness information acquired bythe density unevenness information acquiring unit, and performs N-valuedprocessing (M>N≧2) on the image data based on the determined generationratios.

Since this allows different sizes of dots to be appropriately mixed in aprinted image composed of a plurality of dots, it is possible toeffectively eliminate the banding phenomenon, such as a white streak ora dark streak, which is generated by the so-called flight deflection ordensity unevenness, or make the banding phenomenon nearly inconspicuous.As a result, a high-quality printed material can be obtained easily.

Further, it is possible to eliminate the banding phenomenon or make thebanding phenomenon nearly inconspicuous only in a portion where anydensity unevenness is being caused, by determining the proper generationfrequency of dots having each size for every nozzle according to densityunevenness, and changing the mixing ratio of dots with respect to thatwhen there is no density unevenness.

Further, the term “dot” in the present aspect is a base unitrepresenting characters and figures of a printed material, and means oneregion where ink has reached a recording medium from one nozzle or aplurality of nozzles. Further, a plurality of kinds of this “dot”consist for every size as well as the area having not “zero” but aconstant size (area). Further, the shape of a dot is not necessarilylimited to a true circular shape, but shall also include shapes otherthan the true circular shape, such as an elliptical shape. In this case,since the diameter of the other shapes is not uniform, the dot sizeshall be determined by the area occupied by a dot or based on theaverage diameter of a dot (This is true of the descriptions in thefollowing sections, such as an aspect concerning a “printing apparatus,”an aspect concerning a “printing program,” an aspect concerning a“printing method,” an aspect concerning an “image processing apparatus,”an aspect concerning an “image processing program,” an aspect concerningan “image processing method,” an aspect concerning “recording mediumhaving the program recorded thereon,” and “DESCRIPTION OF EXEMPLARYEMBODIMENTS”).

In addition, if this “dot diameter” is defined more strictly, assumingan equivalent dot in the form a true circle having the area equal to thearea of a dot formed by discharging a certain amount of ink, thediameter of the equivalent dot shall be the dot size. Further,generally, since the absorptivity of ink, etc. will also changedepending on a printing medium, even if the amount of ink is the same,it is a matter of course that, if the recording medium changes, thediameter of a dot to be formed will change in various ways. Further,this “dot” shall not be necessarily limited to a drop formed of a singleink drop by one discharge, and shall also include a drop formed bycombining ink drops by two or more discharges like a very large dot,etc.

Further, “N-valued processing (M>N≧2),” though it will be described infull detail in the following embodiments, is processing which sorts eachpixel into N kinds (M>N≧2) for the image data having M-value (M≧3)density information (for example, 8 bits, 256 gray-scale levels) basedon a certain threshold, and the processing includes the concept that thesize of dots is changed in several stages according to the size of apixel value, other than the so-called “binary” such that a dot isprinted or a dot is not printed (This is true of the descriptions in thefollowing sections, such as an aspect concerning a “printing apparatus,”an aspect concerning a “printing program,” an aspect concerning a“printing method,” an aspect concerning an “image processing apparatus,”an aspect concerning an “image processing program,” an aspect concerningan “image processing method,” an aspect concerning “recording mediumhaving the program recorded thereon,” and “DESCRIPTION OF EXEMPLARYEMBODIMENTS”).

Further, the reason why the value of the “N” is set to “M>N≧2” isbecause, in order to generate the data for printing, it is necessary tospecify at least the binarization on whether a dot is printed or a dotis not printed, and to make the N value smaller than an original pixelvalue (M≧3) of the image data to be processed in terms of the size of adot capable of being printed by a print head (This is true of thedescriptions in the following sections, such as an aspect concerning a“printing apparatus,” an aspect concerning a “printing program,” anaspect concerning a “printing method,” an aspect concerning an “imageprocessing apparatus,” an aspect concerning an “image processingprogram,” an aspect concerning an “image processing method,” an aspectconcerning “recording medium having the program recorded thereon,” and“DESCRIPTION OF EXEMPLARY EMBODIMENTS”).

Further, the “banding phenomenon” shall also include a variation in dotsize caused by the excess and deficiency of the discharge amount of inkfrom a nozzle (of a print head) or the “density unevenness” resultingfrom failed dot printing caused by non-discharge of ink, in addition topoor printing caused by a “white streak” or a “dark streak” generated bythe “flight deflection,” (This is true of the descriptions in thefollowing sections, such as an aspect concerning a “printing apparatus,”an aspect concerning a “printing program,” an aspect concerning a“printing method,” an aspect concerning an “image processing apparatus,”an aspect concerning an “image processing program,” an aspect concerningan “image processing method,” an aspect concerning “recording mediumhaving the program recorded thereon,” and “DESCRIPTION OF EXEMPLARYEMBODIMENTS”).

Further, the “flight deflection” means a phenomenon that a dot may beformed off from its target position due to the fact that, though ink isdischarged, the discharge direction of ink of some of the nozzles isinclined, unlike a mere non-discharge phenomenon of some nozzles asmentioned above (This is true of the descriptions in the followingsections, such as an aspect concerning a “printing apparatus,” an aspectconcerning a “printing program, an aspect concerning a “printingmethod,” an aspect concerning an “image processing apparatus,” an aspectconcerning an “image processing program,” an aspect concerning an “imageprocessing method,” an aspect concerning “recording medium having theprogram recorded thereon,” and “DESCRIPTION OF EXEMPLARY EMBODIMENTS”).

Further, the “white streak” shall also include a portion with lowdensity which may become conspicuous in a streak due to the “densityunevenness” in addition to a portion (region) where the phenomenon thatthe distance between adjacent dots becomes longer than a predetermineddistance is caused continuously due to the “flight deflection,” andconsequently the color of the ground of a printing medium may becomeconspicuous in a streak (This is true of the descriptions in thefollowing sections, such as an aspect concerning a “printing apparatus,”an aspect concerning a “printing program,” an aspect concerning a“printing method,” an aspect concerning an image processing apparatus,”an aspect concerning an “image processing program,” an aspect concerningan “image processing method,” an aspect concerning “recording mediumhaving the program recorded thereon,” and “DESCRIPTION OF EXEMPLARYEMBODIMENTS”).

Further, similarly, the “white streak” shall also include a portion withhigh density which may become conspicuous in a dark streak due to the“flight deflection” in addition to a portion (region) where thephenomenon that the distance between adjacent dots becomes shorter thana predetermined distance is caused continuously due to the “flightdeflection,” and consequently the color of the ground of a printingmedium may become invisible, or the color looks relatively dark when thedistance between dots becomes short, and a portion of a dot formed offfrom its normal position is overlapped with a normal dot, andconsequently the overlapping portion may become conspicuous in a darkstreak (This is true of the descriptions in the following sections, suchas an aspect concerning a “printing apparatus,” an aspect concerning a“printing program,” an aspect concerning a “printing method,” an aspectconcerning an “image processing apparatus,” an aspect concerning an“image processing program,” an aspect concerning an “image processingmethod,” an aspect concerning “recording medium having the programrecorded thereon,” and “DESCRIPTION OF EXEMPLARY EMBODIMENTS”).

Further, the “density unevenness information” of the print head acquiredby the density unevenness information acquiring unit shall also includethe information on the “flight deflection” for every nozzle, that is,the information on the printing deviation amount (difference amount)from an assumed printing position caused by at least the flightdeflection, etc., and a printing deviation direction from an assumedprinting direction, and the information on the deviation amount(difference amount) between an assumed printing dot size and an actualprinting dot size and the deviation amount (difference amount) betweenan assumed ink discharge amount and an actual ink discharge amount, inaddition to the information on the “density unevenness” for every nozzleas mentioned above. That is, there is a deviation of an actual value toeach assumed value as a factor which causes the density unevenness. Asthe amount of this deviation becomes great in a direction in which theprinting density becomes great, the density unevenness also becomesconspicuous (This is true of the descriptions in the following sections,such as an aspect concerning a “printing apparatus,” an aspectconcerning a “printing program, an aspect concerning a “printingmethod,” an aspect concerning an “image processing apparatus,” an aspectconcerning an “image processing program,” an aspect concerning an “imageprocessing method,” an aspect concerning “recording medium having theprogram recorded thereon,” and “DESCRIPTION OF EXEMPLARY EMBODIMENTS”).

Further, the “N-valued data generating unit,” for example, sets apredetermined threshold as a criterion for determination of the densityunevenness, and determines the generation ratio of dots having each sizedepending on whether the acquired density unevenness information exceedsthe threshold, and, if the density unevenness information exceed thethreshold, depending on how much the density unevenness information hasexceeded the threshold. For example, if the acquired density unevennessinformation is smaller than the threshold, the N-valued generating unitmay determine the dot generation ratio so as to be a normal dotgeneration ratio, and if the acquired density unevenness informationexceeds the threshold, the N-valued generating unit may determine thedot generation ratio so that the generation ratio of dots having arelatively large size may become greater than a normal dot generationratio. Further, the N-valued generating unit may determine thegeneration ratio so that, as a value exceeding the threshold becomesgreat, the generation ratio of dots having a relatively large size maybecome great accordingly (This is true of the descriptions in thefollowing sections, such as an aspect concerning a “printing apparatus,”an aspect concerning a “printing program,” an aspect concerning a“printing method,” an aspect concerning an “image processing apparatus,”an aspect concerning an “image processing program,” an aspect concerningan “image processing method,” an aspect concerning “recording mediumhaving the program recorded thereon,” and “DESCRIPTION OF EXEMPLARYEMBODIMENTS”).

Further, for example, in a case in which a print head separately printsthree kinds of sizes of dots including a small dot, a middle dot, and alarge dot, the “generation ratio” is a generation ratio that the numberof small dots to be formed, the number of middle dots to be formed, orthe number of dots to be formed is specified with respect to the totalnumber of print dots formed per unit area in each density value. Forexample, in a case in which the generation ratios of small dots, middledots, and large dots with respect to a certain density value arespecified as 120, 10, and 30, respectively, which size of dots are to beformed with respect to the density value is determined according tothese numbers. Further, the mixing ratio of dots having each size isalso changed by changing this generation ratio. That is, in this aspect,the generation ratio is determined based on the acquired densityunevenness information such that the mixing ratio of dots makes thedensity unevenness inconspicuous (This is true of the descriptions inthe following sections, such as an aspect concerning a “printingapparatus,” an aspect concerning a “printing program,” an aspectconcerning a “printing method,” an aspect concerning an image processingapparatus,” an aspect concerning an “image processing program,” anaspect concerning an “image processing method,” an aspect concerning“recording medium having the program recorded thereon,” and “DESCRIPTIONOF EXEMPLARY EMBODIMENTS”).

Aspect 2:

The printing apparatus of Aspect 2 is a printing apparatus according toAspect 1 in which the information on the density unevenness includes theinformation on a difference value between a density value of a dotformed by each of the nozzles of the print head and an assumed densityvalue.

That is, the density unevenness is a density unevenness which is causedowing to a variation in the performance of the nozzles which constitutesa print head, and a density unevenness which is caused owning to adensity fluctuation which is generated when the density of an actuallyprinted dot exceeds an assumed density or falls below an assumeddensity. Accordingly, in this aspect, since the data on a differencevalue between an actual value and an assumed value of the density inthis density fluctuation is provided as the density unevennessinformation, it is possible to determine a suitable dot generation ratiofor every predetermined region of the image data. Since this allowsdifferent sizes of dots to be appropriately mixed in a printed imagecomposed of a plurality of dots, it is possible to effectively eliminatethe banding phenomenon, such as a white streak or a dark streak, whichis generated by the so-called flight deflection or density unevenness,or make the banding phenomenon nearly inconspicuous. As a result, ahigh-quality printed material can be obtained easily.

Aspect 3:

The printing apparatus of Aspect 3 is a printing apparatus according toAspect 1 or 2 in which, if it is determined that the difference value ofthe density value of the dot to be formed by each of the nozzles of theprint head is greater than a predetermined threshold based on theinformation on the density unevenness, the N-valued data generating unitmakes it greater than that when the generation ratio of large-sized dotsis not determined.

That is, as a difference value between a density value of an actuallyprinted dot and an assumed density value becomes great, the densityunevenness becomes conspicuous. Therefore, for example, in a case inwhich three sizes of dots including a small dot, a middle dot, and alarge dot are separately printed, it is possible to keep the densityunevenness from becoming conspicuous by increasing the generation ratioof the large dot according to the size of the difference value. Sincethis allows different sizes of dots to be appropriately mixed in aprinted image composed of a plurality of dots, it is possible toeffectively eliminate the banding phenomenon, such as a white streak ora dark streak, which is generated by the so-called flight deflection ordensity unevenness, or make the banding phenomenon nearly inconspicuous.As a result, a high-quality printed material can be obtained easily.That is, in a case in which the density unevenness is great, thegranularity will deteriorate because large-sized dots increase byincreasing the generation ratio of the large-sized dots, but the densityunevenness that is a factor of greater image quality deterioration canbe made inconspicuous.

Here, the “relatively large-sized dot” is just a large dot, for example,in the case of three sizes of dots including a small dot, a middle dot,and a large dot as described above, and it may sometimes indicate dotsranging from a maximum size of dot to a dot having a predetermined sizenear the maximum size, such as a maximum size of dot, and a dot having asmaller size than the maximum size, in a case in which dots having moresizes than the three sizes of dots are printed (This is true of thedescriptions in the following sections, such as an aspect concerning a“printing apparatus,” an aspect concerning a “printing program,” anaspect concerning a “printing method,” an aspect concerning an “imageprocessing apparatus,” an aspect concerning an “image processingprogram,” an aspect concerning an “image processing method,” an aspectconcerning “recording medium having the program recorded thereon,” and“DESCRIPTION OF EXEMPLARY EMBODIMENTS”).

Aspect 4:

The printing apparatus of Aspect 4 is a printing apparatus according toAspect 3, further including a density unevenness correcting unit whichcorrects the density value of each pixel of the image data acquired bythe image data acquiring unit based on the density unevennessinformation acquired by the density unevenness information acquiringunit. The N-valued data generating unit is adapted to perform N-valuedprocessing on the image data corrected by the density unevennesscorrecting unit to generate N-valued data.

That is, this aspect further includes a density unevenness correctingunit in addition to the configuration of Aspect 3, and is adapted tocorrect the density value of each pixel of the image data acquired bythe image data acquiring unit based on the density unevennessinformation acquired by the density unevenness information acquiringunit, using this density unevenness correcting unit, and thereafter, toperform N-valued processing.

That is, since the generation ratio is determined after the densityunevenness has been corrected in advance by subtracting and adding adifference value between an actual value and an assumed value to/fromeach pixel value of image data, the generation ratio of large-sized dotsin a portion which cannot be corrected by the density correctionprocessing can be increased. Thus, a portion recognized as the densityunevenness becomes less than when the generation ratio is determinedwithout correction (or the size of the density unevenness becomessmall). Therefore, it is possible to relatively reduce the increasingamount of large-sized dots. Since this can effectively eliminate thebanding phenomenon, such as a white streak or a dark streak, which isgenerated by the so-called flight deflection or density unevenness, ormake the banding phenomenon nearly inconspicuous, and can also reducedeterioration of granularity, a higher-quality printed material can beobtained.

Aspect 5:

The printing apparatus of Aspect 5 is a printing apparatus according toAspect 3, further including a dot ratio information storing unit whichstores dot ratio information which specifies the mixing ratios of thedifferent sizes of dots, and a dot ratio information selecting unitwhich selects a predetermined item of dot ratio information among thedot ratio information stored in the dot ratio information storing unitbased on the density unevenness information acquired by the densityunevenness information acquiring unit. Here, the N-valued datagenerating unit determines the generation ratios of the different sizesof dots for every predetermined region of the image data acquired by theimage data acquiring unit based on the dot ratio information selected bythe dot ratio information selecting unit, and performs N-valuedprocessing (M>N≧2) on the image data based on the determined generationratios.

That is, this aspect further includes a dot ratio information storingunit and a dot ratio information selecting unit in addition to theconfiguration of Aspect 3, and is adapted to perform N-valued processingon the image data acquired by the image data acquiring unit so that itmay become a generation ratio (dot mixing ratio) specified in the dotratio information selected by the dot ratio information selecting unit.

That is, the generation ratio can be simply determined only by preparinga plurality of kinds of dot ratio information in advance according tosituations of occurrence of the density unevenness, and selecting thedot ratio information corresponding to the acquired density unevennessinformation from the plurality of kinds of dot ratio information. Sincethis allows N-valued processing to be efficiently performed according toa generation ratio specified in the selected dot ratio information, itis possible to more efficiently eliminate the banding phenomenon or makethe banding phenomenon nearly inconspicuous.

Here, as the “method of selecting dot ratio information”, the thresholdwhich determines a normal value and an abnormal value is set in advancefor the numerical values which show the density unevenness, and typicaldot ratio information is selected or abnormal dot ratio information isselected depending on whether or not a value exceeds the threshold. Thisthreshold is set, for example, for every plural kinds of dot ratioinformation, and for example, the dot ratio information of the greatestthreshold among exceeding thresholds is selected (This is true of thedescriptions in the following sections, such as an aspect concerning a“printing apparatus,” an aspect concerning a “printing program,” anaspect concerning a “printing method,” an aspect concerning an “imageprocessing apparatus,” an aspect concerning an “image processingprogram,” an aspect concerning an “image processing method,” an aspectconcerning “recording medium having the program recorded thereon,” and“DESCRIPTION OF EXEMPLARY EMBODIMENTS”).

Further, the “dot ratio information” may be prepared, for example, inunits of a nozzle, and may be prepared in units of plural nozzles (forexample, a target nozzle and nozzles in the vicinity of the targetnozzle). For example, in a case in which the dot ratio information isprepared in units of a nozzle, the dot ratio information is selected forevery corresponding pixel, and in a case in which the dot ratioinformation is prepared in units of plural nozzles, the dot ratioinformation is selected for every corresponding plural pixels (This istrue of the descriptions in the following sections, such as an aspectconcerning a “printing apparatus,” an aspect concerning a “printingprogram,” an aspect concerning a “printing method,” an aspect concerningan “image processing apparatus,” an aspect concerning an “imageprocessing program,” an aspect concerning an “image processing method,”an aspect concerning “recording medium having the program recordedthereon,” and “DESCRIPTION OF EXEMPLARY EMBODIMENTS”).

Aspect 6:

The printing apparatus of Aspect 6 is a printing apparatus according toAspect 3, further including a density unevenness correcting unit whichcorrects the density value of each pixel of the image data acquired bythe image data acquiring unit based on the density unevennessinformation acquired by the density unevenness information acquiringunit, a dot ratio information storing unit which stores dot ratioinformation which specifies the mixing ratios of the different sizes ofdots, and a dot ratio information selecting unit which selects apredetermined item of dot ratio information among the dot ratioinformation stored in the dot ratio information storing unit based onthe density unevenness information acquired by the density unevennessinformation acquiring unit. Here, the N-valued data generating unitdetermines the generation ratios of the different sizes of dots forevery predetermined region of the image data corrected by the densityunevenness correcting unit based on the dot ratio information selectedby the dot ratio information selecting unit, and performs N-valuedprocessing (M>N≧2) on the image data based on the determined generationratios.

That is, this aspect further includes a density unevenness correctingunit, a dot ratio information storing unit, and a dot ratio informationselecting unit in addition to the configuration of Aspect 3, and isadapted to perform N-valued processing on the image data acquired by theimage data acquiring unit so that it may become a generation ratio (dotmixing ratio) specified in the dot ratio information after the pixelvalue of the image data corresponding to a nozzle which causes densityunevenness has been corrected in advance like Aspect 3.

That is, since the generation ratio is determined after the densityunevenness has been corrected in advance by subtracting and adding adifference value between an actual value and an assumed value to/fromeach pixel value of image data, the generation ratio of large-sized dotsin a portion which cannot be corrected by the density correctionprocessing can be increased. Thus, a portion recognized as the densityunevenness becomes less than when the generation ratio is determinedwithout correction (or the size of the density unevenness becomessmall). Therefore, it is possible to relatively reduce the increasingamount of large-sized dots. Since this can effectively eliminate thebanding phenomenon, such as a white streak or a dark streak, which isgenerated by the so-called flight deflection or density unevenness, ormake the banding phenomenon nearly inconspicuous, and can also reducedeterioration of granularity, a higher-quality printed material can beobtained.

That is, the generation ratio can be simply determined only by preparinga plurality of kinds of dot ratio information in advance according tosituations of occurrence of the density unevenness, and selecting thedot ratio information corresponding to the acquired density unevennessinformation from the plurality of kinds of dot ratio information. Sincethis allows N-valued processing to be efficiently performed according toa generation ratio specified in the selected dot ratio information, itis possible to more efficiently eliminate the banding phenomenon or makethe banding phenomenon nearly inconspicuous.

Aspect 7:

The printing apparatus of Aspect 7 is a printing apparatus according toAspect 4 or 5, in which the dot ratio information selecting unit isadapted to select a predetermined item of dot ratio information from thedot ratio information stored in the dot ratio information storing unitfor every plural nozzles including a target nozzle of the print head,and nozzles in the vicinity of the target nozzle. Since this allows thegeneration ratio (dot mixing ratio) to be determined in units of pluralnozzles including a target nozzle of a print head and about two to tennozzles before and after the target nozzle, it is possible to moreeffectively eliminate the banding phenomenon resulting from the densityunevenness as well as the flight deflection or make the bandingphenomenon nearly inconspicuous.

That is, in a case in which processing is performed so that thegeneration ratio of large-sized dots may become great only on a line ofa target nozzle, there is a case that the density unevenness cannot beeliminated from the relationship (for example, further away than whenthe distance between dots has not been determined) to its peripheralline. Even in such a case, in this aspect, the generation ratio isdetermined for every region including a line to be formed by a nozzle(target nozzle) which causes density unevenness and a line to be formedby a nozzle in the vicinity of the target nozzle. Thus, a lot ofrelatively large-sized dots are formed not only in a target line butalso in the lines at both sides of the target line. Thus, thesesynergetic effects can eliminate the density unevenness which cannot beeliminated only with the target line.

Aspect 8:

The printing apparatus of Aspect 8 is a printing apparatus according toany one of Aspects 4 to 6, in which the dot ratio information selectingunit is adapted to select a predetermined item of dot ratio informationamong the dot ratio information stored in the dot ratio informationstoring unit based on the information on a printing position deviationamount of the print head among the density unevenness informationacquired by the density unevenness information acquiring unit. Sincethis allows optimal processing to be performed based on the flightdeflection amount (the deviation amount from an assumed printingposition), it is possible to effectively eliminate the bandingphenomenon or make the banding phenomenon nearly inconspicuous whileavoiding deterioration of image quality.

Aspect 9:

The printing apparatus of Aspect 9 is a printing apparatus according toany one of Aspects 4 to 6, in which the dot ratio information selectingunit is adapted to select two or more kinds of dot ratio informationamong the dot ratio information stored in the dot ratio informationstoring unit based on the information on a printing position deviationamount of the print head among the density unevenness informationacquired by the density unevenness information acquiring unit, and inwhich the N-valued data generating unit determines the generation ratiosof the different sizes of dots for every predetermined region of theimage data based on the two or more kinds of dot ratio informationselected by the dot ratio information selecting unit, and performsN-valued processing (M>N≧2) on the image data based on the determinedgeneration ratios. Thereby, in a case in which the banding phenomenon iscaused in a plurality of places within one processing region, optimalprocessing according to the degree in each place can be performed.Therefore, it is possible to effectively eliminate the bandingphenomenon or make the banding phenomenon nearly inconspicuous whileavoiding deterioration of image quality.

Here, the “based on two or more kinds of dot ratio information” meansthat, for example, in a case in which there is two kinds of dot ratioinformation, these two kinds of dot ratio information are mixedtogether, thereby a piece of dot ratio information having anintermediate characteristic of the two kinds of dot ratio information isgenerated, and the generated dot ratio information becomes a basis.Further, in a case in which there are three or more kinds of dot ratioinformation, two or more kinds of dot ratio information are selectedfrom the three or more kinds of dot ratio information according todensity unevenness information, and the two or more kinds of selecteddot ratio information are mixed, thereby generating the dot ratioinformation having an intermediate characteristic of the two or morekinds of selected dot ratio information. Further, as well as mixing dotratio information to generate new information, the use ratio of two ormore kinds of dot ratio information may be determined so that two ormore kinds of dot ratio information can be used in this determined useratio. Further, for example, in a case in which the use ratio of twopieces of dot ratio information is set to 50%, the generation ratio isdetermined for every predetermined region of image data by using thesetwo pieces of dot ratio information by turns (This is true of thedescriptions in the following sections, such as an aspect concerning a“printing apparatus,” an aspect concerning a “printing program,” anaspect concerning a “printing method,” an aspect concerning an “imageprocessing apparatus,” an aspect concerning an “image processingprogram,” an aspect concerning an “image processing method,” an aspectconcerning “recording medium having the program recorded thereon,” and“DESCRIPTION OF EXEMPLARY EMBODIMENTS”).

Aspect 10:

Further, according to Aspect 10 of the invention, there is provided aprinting program which causes a computer to function as: an image dataacquiring unit which acquires image data having M-value densityinformation (M≧3) for every pixel; a density unevenness informationacquiring unit which acquires information on the density unevenness ofthe nozzles which can print different sizes of dots; an N-valued datagenerating unit which performs N-valued processing (M>N≧2) on the imagedata acquired by the image data acquiring unit to generate N-valueddata; a print data generating unit which generates print data from theN-valued data generated by the N-valued data generating unit; and aprinting unit which performs printing based on the print data generatedby the print data generating unit. Here, the program causes the N-valueddata generating unit to function to determine the generation ratios ofthe different sizes of dots for every predetermined region of the imagedata acquired by the image data acquiring unit based on the densityunevenness information acquired by the density unevenness informationacquiring unit, and to perform N-valued processing (M>N≧2) on the imagedata based on the determined generation ratios.

This, similar to Aspect 1, can effectively eliminate the bandingphenomenon, such as a white streak or a dark streak, which is generatedby the so-called flight deflection or density unevenness, or make thebanding phenomenon nearly inconspicuous. As a result, a high-qualityprinted material can be obtained. Further, it is possible to eliminatethe banding phenomenon or make the banding phenomenon nearlyinconspicuous only in a portion where any density unevenness is beingcaused, by determining the proper generation frequency of dots havingeach size for every nozzle according to density unevenness, and changingthe mixing ratio of dots with respect to that when there is no densityunevenness.

Further, since most of printing apparatuses that are presently on themarket, such as ink jet printers, includes a computer system composed ofa central processing unit (CPU), storage devices (RAM, ROM),input/output devices, etc., and the above respective units can berealized by software using this computer system, these respective unitscan be realized economically and easily compared with a case where theabove respective units can be realized by making exclusive hardware.Furthermore, upgrade by alterations, improvements, etc. of functions canalso be easily performed by rewriting a portion of the program.

Aspect 11:

The printing program of Aspect 11 is a printing program according toAspect 10 in which the information on the density unevenness includesthe information on a difference value between a density value of a dotformed by each of the nozzles of the print head and an assumed densityvalue.

Since this allows different sizes of dots to be more appropriately mixedin a printed image composed of a plurality of dots similarly to Aspect2, it is possible to effectively eliminate the banding phenomenon, suchas a white streak or a dark streak, which is generated by the so-calledflight deflection or density unevenness, or make the banding phenomenonnearly inconspicuous. As a result, a high-quality printed material canbe obtained easily.

Further, similar to Aspect 10, since the above respective units can berealized using a computer system provided standard in most of printingapparatuses that are presently on the market, such as ink jet printers,the above respective units can be realized economically and easilycompared with a case where the above respective units can be realized bymaking exclusive hardware. Furthermore, upgrade by alterations,improvements, etc. of functions can also be easily performed byrewriting a portion of the program.

Aspect 12:

The printing program of Aspect 12 is a printing program according toAspect 10 or 12, in which, if it is determined that the difference valueof the density value of the dot to be formed by each of the nozzles ofthe print head is greater than a predetermined threshold based on theinformation on the density unevenness, the N-valued data generating unitmakes it greater than that when the generation ratio of large-sized dotsis not determined.

Since this allows different sizes of dots to be more appropriately mixedin a printed image composed of a plurality of dots similarly to Aspect3, it is possible to effectively eliminate the banding phenomenon, suchas a white streak or a dark streak, which is generated by the so-calledflight deflection or density unevenness, or make the banding phenomenonnearly inconspicuous. As a result, a high-quality printed material canbe obtained easily.

Further, similar to Aspect 10, since the above respective units can berealized using a computer system provided standard in most of printingapparatuses that are presently on the market, such as ink jet printers,the above respective units can be realized economically and easilycompared with a case where the above respective units can be realized bymaking exclusive hardware. Furthermore, upgrade by alterations,improvements, etc. of functions can also be easily performed byrewriting a portion of the program.

Aspect 13:

The printing program of Aspect 13 is a printing program according toAspect 12 causing a computer to function as a density unevennesscorrecting unit which corrects the density value of each pixel of theimage data acquired by the image data acquiring unit based on thedensity unevenness information acquired by the density unevennessinformation acquiring unit. The N-valued data generating unit performsN-valued processing on the image data corrected by the densityunevenness correcting unit to generate N-valued data.

Since this, similar to Aspect 4, can effectively eliminate the bandingphenomenon, such as a white streak or a dark streak, which is generatedby the so-called flight deflection or density unevenness, or make thebanding phenomenon nearly inconspicuous, and can also reducedeterioration of granularity, a higher-quality printed material can beobtained.

Further, similar to Aspect 10, since the above respective units can berealized using a computer system provided standard in most of printingapparatuses, the above respective units can be realized economically andeasily compared with a case where the above respective units can berealized by making exclusive hardware. Furthermore, upgrade byalterations, improvements, etc. of functions can also be easilyperformed by rewriting a portion of the program.

Aspect 14:

The printing program of Aspect 14 is a printing program according toAspect 12, causing a computer to function as a dot ratio informationstoring unit which stores dot ratio information which specifies themixing ratios of the different sizes of dots, a dot ratio informationselecting unit which selects a predetermined item of dot ratioinformation among the dot ratio information stored in the dot ratioinformation storing unit based on the density unevenness informationacquired by the density unevenness information acquiring unit. Here, theN-valued data generating unit determines the generation ratios of thedifferent sizes of dots for every predetermined region of the image dataacquired by the image data acquiring unit based on the dot ratioinformation selected by the dot ratio information selecting unit, andperforms N-valued processing (M>N≧2) on the image data based on thedetermined generation ratios.

Since this, similar to Aspect 5, allows N-valued processing to beefficiently performed according to a generation ratio specified in theselected dot ratio information, it is possible to more efficientlyeliminate the banding phenomenon or make the banding phenomenon nearlyinconspicuous.

Further, similar to Aspect 10, since the above respective units can berealized using a computer system provided standard in most of printingapparatuses, the above respective units can be realized economically andeasily compared with a case where the above respective units can berealized by making exclusive hardware. Furthermore, upgrade byalterations, improvements, etc. of functions can also be easilyperformed by rewriting a portion of the program.

Aspect 15:

The printing program of Aspect 15 is a printing program according toAspect 12, causing a computer to function as density unevennesscorrecting unit which corrects the density value of each pixel of theimage data acquired by the image data acquiring unit based on thedensity unevenness information acquired by the density unevennessinformation acquiring unit, a dot ratio information storing unit whichstores dot ratio information which specifies the mixing ratios of thedifferent sizes of dots, and a dot ratio information selecting unitwhich selects a predetermined item of dot ratio information among thedot ratio information stored in the dot ratio information storing unitbased on the density unevenness information acquired by the densityunevenness information acquiring unit. Here, the N-valued datagenerating unit determines the generation ratios of the different sizesof dots for every predetermined region of the image data corrected bythe density unevenness correcting unit based on the dot ratioinformation selected by the dot ratio information selecting unit, andperforms N-valued processing (M>N≧2) on the image data based on thedetermined generation ratios.

Since this, similar to Aspect 6, can effectively eliminate the bandingphenomenon, such as a white streak or a dark streak, which is generatedby the so-called flight deflection or density unevenness, or make thebanding phenomenon nearly inconspicuous, and can also reducedeterioration of granularity, a higher-quality printed material can beobtained. Further, since this allows N-valued processing to beefficiently performed according to a generation ratio specified in theselected dot ratio information, it is possible to more efficientlyeliminate the banding phenomenon or make the banding phenomenon nearlyinconspicuous.

Further, similar to Aspect 10, since the above respective units can berealized using a computer system provided standard in most of printingapparatuses, the above respective units can be realized economically andeasily compared with a case where the above respective units can berealized by making exclusive hardware. Furthermore, upgrade byalterations, improvements, etc. of functions can also be easilyperformed by rewriting a portion of the program.

Aspect 16:

The printing program of Aspect 16 is a printing program according toAspect 13 or 14, in which the dot ratio information selecting unitselects a predetermined item of dot ratio information from the dot ratioinformation stored in the dot ratio information storing unit for everyplural nozzles including a target nozzle of the print head, and nozzlesin the vicinity of the target nozzle.

Since this, similar to Aspect 7, allows the generation ratio (dot mixingratio) to be determined in units of plural nozzles including a targetnozzle of a print head and about two to ten nozzles before and after thetarget nozzle, it is possible to more effectively eliminate the bandingphenomenon resulting from the density unevenness as well as the flightdeflection or make the banding phenomenon nearly inconspicuous.

Further, similar to Aspect 10, since the above respective units can berealized using a computer system provided standard in most of printingapparatuses, the above respective units can be realized economically andeasily compared with a case where the above respective units can berealized by making exclusive hardware. Furthermore, upgrade byalterations, improvements, etc. of functions can also be easilyperformed by rewriting a portion of the program.

Aspect 17:

The printing program of Aspect 17 is a printing program according to anyone of Aspects 13 to 15, in which the dot ratio information selectingunit selects a predetermined item of dot ratio information among the dotratio information stored in the dot ratio information storing unit basedon the information on a printing position deviation amount of the printhead among the density unevenness information acquired by the densityunevenness information acquiring unit.

Since this, similar to Aspect 8, allows optimal processing to beperformed based on the flight deflection amount (the deviation amountfrom an assumed printing position), it is possible to effectivelyeliminate the banding phenomenon or make the banding phenomenon nearlyinconspicuous while avoiding deterioration of image quality.

Further, similar to Aspect 10, since the above respective units can berealized using a computer system provided standard in most of printingapparatuses, the above respective units can be realized economically andeasily compared with a case where the above respective units can berealized by making exclusive hardware. Furthermore, upgrade byalterations, improvements, etc. of functions can also be easilyperformed by rewriting a portion of the program.

Aspect 18:

The printing program of Aspect 18 is a printing program according to anyone of Aspects 13 to 15, in which the dot ratio information selectingunit selects two or more kinds of dot ratio information among the dotratio information stored in the dot ratio information storing unit basedon the information on a printing position deviation amount of the printhead among the density unevenness information acquired by the densityunevenness information acquiring unit, and in which the N-valued datagenerating unit determines the generation ratios of the different sizesof dots for every predetermined region of the image data based on thetwo or more kinds of dot ratio information selected by the dot ratioinformation selecting unit, and performs N-valued processing (M>N≧2) onthe image data based on the determined generation ratios.

Thereby, similar to Aspect 9, in a case in which the banding phenomenonis caused in a plurality of places within one processing region, optimalprocessing according to the degree in each place can be performed.Therefore, it is possible to effectively eliminate the bandingphenomenon or make the banding phenomenon nearly inconspicuous whileavoiding deterioration of image quality.

Further, similar to Aspect 10, since the above respective units can berealized using a computer system provided standard in most of printingapparatuses, the above respective units can be realized economically andeasily compared with a case where the above respective units can berealized by making exclusive hardware. Furthermore, upgrade byalterations, improvements, etc. of functions can also be easilyperformed by rewriting a portion of the program.

Aspect 19:

A computer-readable recording medium of Aspect 19 is a computer-readablerecording medium on which the printing program according to any oneAspects 10 to 18 is recorded.

This makes it possible to easily and certainly provide the programaccording to any one of Aspect 10 to 18 to consumers, such as users, bycomputer-readable storage media, such as CD-ROMs, DVD-ROMs, FDs,semiconductor chips.

Aspect 20:

Further, according to Aspect 20 of the invention, there is provided aprinting method including: acquiring image data having M-value densityinformation (M≧3) for every pixel; acquiring the information on thedensity unevenness of nozzles which can print different sizes of dots;performing N-valued processing (M>N≧2) on the image data acquired in theacquiring of the image data to generate N-valued data; generating printdata from the N-valued data generated in the generating of the N-valueddata; and performing printing using the print head based on the printdata generated in the generating of the print data. Here, in thegenerating of the N-valued data, the generation ratios of the differentsizes of dots is determined for every predetermined region of the imagedata acquired in the generating of the image data based on the densityunevenness information acquired in the acquiring of the densityunevenness information, and N-value processing (M>N≧2) is performed onthe image data based on the determined generation ratios.

This, similar to Aspect 1, can effectively eliminate the bandingphenomenon, such as a white streak or a dark streak, which is generatedby the so-called flight deflection or density unevenness, or make thebanding phenomenon nearly inconspicuous. As a result, a high-qualityprinted material can be obtained.

Further, it is possible to eliminate the banding phenomenon or make thebanding phenomenon nearly inconspicuous only in a portion where anydensity unevenness is being caused, by determining the proper generationfrequency of dots having each size for every nozzle according to densityunevenness, and changing the mixing ratio of dots with respect to thatwhen there is no density unevenness.

Aspect 21:

The printing method of Aspect 21 is a printing method according toAspect 20 in which the information on the density unevenness includesthe information on a difference value between a density value of a dotformed by each of the nozzles of the print head and an assumed densityvalue.

Since this, similar to Aspect 2, allows different sizes of dots to bemore appropriately mixed in a printed image composed of a plurality ofdots, it is possible to effectively eliminate the banding phenomenon,such as a white streak or a dark streak, which is generated by theso-called flight deflection or density unevenness, or make the bandingphenomenon nearly inconspicuous. As a result, a high-quality printedmaterial can be obtained easily.

Aspect 22:

The printing method of Aspect 22 is a printing method according to 20 or21 in which, if it is determined in the generating of the N-valued datathat the difference value of the density value of the dot to be formedby each of the nozzles of the print head is greater than a predeterminedthreshold based on the information on the density unevenness, it is madegreater than that when the generation ratio of large-sized dots is notdetermined.

Since this, similar to Aspect 3, allows different sizes of dots to bemore appropriately mixed in a printed image composed of a plurality ofdots, it is possible to effectively eliminate the banding phenomenon,such as a white streak or a dark streak, which is generated by theso-called flight deflection or density unevenness, or make the bandingphenomenon nearly inconspicuous. As a result, a high-quality printedmaterial can be obtained easily.

Aspect 23:

The printing method of Aspect 23 is a printing method according toAspect 22, further including correcting the density value of each pixelof the image data acquired in the acquiring of the image data based onthe density unevenness information acquired in the acquiring of thedensity unevenness information. In the generating of the N-valued data,N-valued processing is performed on the image data corrected in thecorrecting of the density unevenness to generate N-valued data.

Since this, similar to Aspect 4, can effectively eliminate the bandingphenomenon, such as a white streak or a dark streak, which is generatedby the so-called flight deflection or density unevenness, or make thebanding phenomenon nearly inconspicuous, and can also reducedeterioration of granularity, a higher-quality printed material can beobtained.

Aspect 24:

The printing method of Aspect 24 is a printing method according toAspect 22, further including storing dot ratio information whichspecifies the mixing ratios of the different sizes of dots, selecting apredetermined item of dot ratio information among the dot ratioinformation stored in the storing of the dot ratio information based onthe density unevenness information acquired in the acquiring of thedensity unevenness information. Here, in the generating of the N-valueddata, the generation ratios of the different sizes of dots is determinedfor every predetermined region of the image data acquired in theacquiring of the image data based on the dot ratio information selectedin the selecting of the dot ratio information, and N-valued processing(M>N≧2) is performed on the image data based on the determinedgeneration ratios.

Since this, similar to Aspect 5, allows N-valued processing to beefficiently performed according to a generation ratio specified in theselected dot ratio information, it is possible to more efficientlyeliminate the banding phenomenon or make the banding phenomenon nearlyinconspicuous.

Aspect 25:

The printing program of Aspect 25 is a printing program according toAspect 12, correcting the density value of each pixel of the image dataacquired in the acquiring of the image data based on the densityunevenness information acquired in the acquiring of the densityunevenness information, storing dot ratio information which specifiesthe mixing ratios of the different sizes of dots, and selecting apredetermined item of dot ratio information among the dot ratioinformation stored in the storing of the dot ratio information based onthe density unevenness information acquired in the acquiring of thedensity unevenness information. Here, in the generating of the N-valueddata, the generation ratios of the different sizes of dots is determinedfor every predetermined region of the image data corrected in thecorrecting of the density unevenness based on the dot ratio informationselected in the selecting of the dot ratio information, and N-valuedprocessing (M>N≧2) is performed on the image data based on thedetermined generation ratios.

Since this, similar to Aspect 6, can effectively eliminate the bandingphenomenon, such as a white streak or a dark streak, which is generatedby the so-called flight deflection or density unevenness, or make thebanding phenomenon nearly inconspicuous, and can also reducedeterioration of granularity, a higher-quality printed material can beobtained. Further, since this allows N-valued processing to beefficiently performed according to a generation ratio specified in theselected dot ratio information, it is possible to more efficientlyeliminate the banding phenomenon or make the banding phenomenon nearlyinconspicuous.

Aspect 26:

The printing method of Aspect 26 is a printing method according toAspect 23 or 24, in which, in the selecting of the dot ratioinformation, a predetermined item of dot ratio information is selectedfrom the dot ratio information stored in the storing of the dot ratioinformation for every plural nozzles including a target nozzle of theprint head, and nozzles in the vicinity of the target nozzle.

Since this, similar to Aspect 7, allows the generation ratio (dot mixingratio) to be determined in units of plural nozzles including a targetnozzle of a print head and about two to ten nozzles before and after thetarget nozzle, it is possible to more effectively eliminate the bandingphenomenon resulting from the density unevenness as well as the flightdeflection or make the banding phenomenon nearly inconspicuous.

Aspect 27:

The printing method of Aspect 27 is a printing method according to anyone of Aspects 23 to 25, in which, in the selecting of the dot ratioinformation, a predetermined item of dot ratio information is selectedfrom the dot ratio information stored in the storing of the dot ratioinformation based on the information on a printing position deviationamount of the print head among the density unevenness informationacquired in the acquiring of the density unevenness information.

Since this, similar to Aspect 8, allows optimal processing to beperformed based on the flight deflection amount (the deviation amountfrom an assumed printing position), it is possible to effectivelyeliminate the banding phenomenon or make the banding phenomenon nearlyinconspicuous while avoiding deterioration of image quality.

Aspect 28:

The printing method of Aspect 28 is a printing method according to anyone of Aspects 13 to 15, in which, in the selecting of the dot ratioinformation, two or more kinds of dot ratio information is selected fromthe dot ratio information stored in the storing of the dot ratioinformation based on the information on a printing position deviationamount of the print head among the density unevenness informationacquired in the acquiring of the density unevenness information, and inwhich, in the generating of the N-valued data, the generation ratios ofthe different sizes of dots is determined for every predetermined regionof the image data based on the two or more kinds of dot ratioinformation selected in the selecting of the dot ratio information, andN-valued processing (M>N≧2) is performed on the image data based on thedetermined generation ratios.

Thereby, similar to Aspect 9, in a case in which the banding phenomenonis caused in a plurality of places within one processing region, optimalprocessing according to the degree in each place can be performed.Therefore, it is possible to effectively eliminate the bandingphenomenon or make the banding phenomenon nearly inconspicuous whileavoiding deterioration of image quality.

Aspect 29:

Further, according to Aspect 29 of the invention, there is provided animage processing apparatus including: an image data acquiring unit whichacquires image data having M-value density information (M≧3) for everypixel; a density unevenness information acquiring unit which acquiresinformation on the density unevenness of the nozzles which can printdifferent sizes of dots; an N-valued data generating unit which performsN-valued processing (M>N≧2) on the image data acquired by the image dataacquiring unit to generate N-valued data; a print data generating unitwhich generates print data from the N-valued data generated by theN-valued data generating unit; and a printing unit which performsprinting based on the print data generated by the print data generatingunit. Here, the N-valued data generating unit determines the generationratios of the different sizes of dots for every predetermined region ofthe image data acquired by the image data acquiring unit based on thedensity unevenness information acquired by the density unevennessinformation acquiring unit, and performs N-valued processing (M>N≧2) onthe image data based on the determined generation ratios.

This, similar to Aspect 1, makes it possible to generate print datawhich effectively eliminate the banding phenomenon, such as a whitestreak or a dark streak, which is generated by the so-called flightdeflection or density unevenness, or make the banding phenomenon nearlyinconspicuous.

Further, since the above respective units can be realized using ageneral-purpose computer system, such as a personal computer (PC), theabove respective units can be realized economically and easily comparedwith a case where the above respective units can be realized by makingexclusive hardware. Furthermore, upgrade by alterations, improvements,etc. of functions can also be easily performed by rewriting a portion ofthe program (this is true of the following aspect concerning an imageprocessing apparatus).

Aspect 30:

The image processing apparatus of Aspect 30 is an image processingapparatus according to Aspect 29 in which the information on the densityunevenness includes the information on a difference value between adensity value of a dot formed by each of the nozzles of the print headand an assumed density value.

Since this, similar to Aspect 2, allows different sizes of dots to bemore appropriately mixed in a printed image composed of a plurality ofdots, it is possible to generate print data which can effectivelyeliminate the banding phenomenon, such as a white streak or a darkstreak, which is generated by the so-called flight deflection or densityunevenness, or make the banding phenomenon nearly inconspicuous.

Aspect 31:

The image processing apparatus of Aspect 31 is an image processingapparatus according to 29 or 30 in which, if it is determined that thedifference value of the density value of the dot to be formed by each ofthe nozzles of the print head is greater than a predetermined thresholdbased on the information on the density unevenness, the N-valued datagenerating unit makes it greater than that when the generation ratio oflarge-sized dots is not determined.

Since this, similar to Aspect 3, allows different sizes of dots to bemore appropriately mixed in a printed image composed of a plurality ofdots, it is possible to generate print data which can effectivelyeliminate the banding phenomenon, such as a white streak or a darkstreak, which is generated by the so-called flight deflection or densityunevenness, or make the banding phenomenon nearly inconspicuous.

Aspect 32:

The image processing apparatus of Aspect 32 is an image processingapparatus according to Aspect 31, further including a density unevennesscorrecting unit which corrects the density value of each pixel of theimage data acquired by the image data acquiring unit based on thedensity unevenness information acquired by the density unevennessinformation acquiring unit. The N-valued data generating unit performsN-valued processing on the image data corrected by the densityunevenness correcting unit to generate N-valued data.

This, similar to Aspect 4, makes it possible to generate whicheffectively eliminate the banding phenomenon, such as a white streak ora dark streak, which is generated by the so-called flight deflection ordensity unevenness, or make the banding phenomenon nearly inconspicuous,and can also reduce deterioration of granularity.

Aspect 33:

The image processing apparatus of Aspect 33 is an image processingapparatus according to Aspect 31, further including a dot ratioinformation storing unit which stores dot ratio information whichspecifies the mixing ratios of the different sizes of dots, a dot ratioinformation selecting unit which selects a predetermined item of dotratio information among the dot ratio information stored in the dotratio information storing unit based on the density unevennessinformation acquired by the density unevenness information acquiringunit. Here, the N-valued data generating unit determines the generationratios of the different sizes of dots for every predetermined region ofthe image data acquired by the image data acquiring unit based on thedot ratio information selected by the dot ratio information selectingunit, and performs N-valued processing (M>N≧2) on the image data basedon the determined generation ratios.

Since this, similar to Aspect 5, allows N-valued processing to beefficiently performed according to a generation ratio specified in theselected dot ratio information, it is possible to generate print datawhich more efficiently eliminate the banding phenomenon or make thebanding phenomenon nearly inconspicuous.

Aspect 34:

The image processing apparatus of Aspect 34 is an image processingapparatus according to Aspect 31, further including a density unevennesscorrecting unit which corrects the density value of each pixel of theimage data acquired by the image data acquiring unit based on thedensity unevenness information acquired by the density unevennessinformation acquiring unit, a dot ratio information storing unit whichstores dot ratio information which specifies the mixing ratios of thedifferent sizes of dots, and a dot ratio information selecting unitwhich selects a predetermined item of dot ratio information among thedot ratio information stored in the dot ratio information storing unitbased on the density unevenness information acquired by the densityunevenness information acquiring unit. Here, the N-valued datagenerating unit determines the generation ratios of the different sizesof dots for every predetermined region of the image data corrected bythe density unevenness correcting unit based on the dot ratioinformation selected by the dot ratio information selecting unit, andperforms N-valued processing (M>N≧2) on the image data based on thedetermined generation ratios.

Since this, similar to Aspect 6, can effectively eliminate the bandingphenomenon, such as a white streak or a dark streak, which is generatedby the so-called flight deflection or density unevenness, or make thebanding phenomenon nearly inconspicuous, and can also reducedeterioration of granularity, a higher-quality printed material can beobtained. Further, since N-valued processing can be efficientlyperformed according to a generation ratio specified in the selected dotratio information, it is possible to generate print data which moreefficiently eliminate the banding phenomenon or make the bandingphenomenon nearly inconspicuous.

Aspect 35:

The image processing apparatus of Aspect 35 is an image processingapparatus according to Aspect 32 or 33, in which the dot ratioinformation selecting unit selects a predetermined item of dot ratioinformation from the dot ratio information stored in the dot ratioinformation storing unit for every plural nozzles including a targetnozzle of the print head, and nozzles the vicinity of the target nozzle.

Since this, similar to Aspect 7, allows the generation ratio (dot mixingratio) to be determined in units of plural nozzles including a targetnozzle of a print head and about two to ten nozzles before and after thetarget nozzle, it is possible to generate print data which can moreeffectively eliminate the banding phenomenon resulting from the densityunevenness as well as the flight deflection or make the bandingphenomenon nearly inconspicuous.

Aspect 36:

The image processing apparatus of Aspect 36 is an image processingapparatus according to any one of Aspects 32 to 34, in which the dotratio information selecting unit selects a predetermined item of dotratio information among the dot ratio information stored in the dotratio information storing unit based on the information on a printingposition deviation amount of the print head among the density unevennessinformation acquired by the density unevenness information acquiringunit.

Since this, similar to Aspect 8, allows optimal processing to beperformed based on the flight deflection amount (the deviation amountfrom an assumed printing position), it is possible to generate printdata which effectively eliminate the banding phenomenon or make thebanding phenomenon nearly inconspicuous while avoiding deterioration ofimage quality.

Aspect 37:

The image processing apparatus of Aspect 37 is an image processingapparatus according to any one of Aspects 32 to 34, in which the dotratio information selecting unit selects two or more kinds of dot ratioinformation among the dot ratio information stored in the dot ratioinformation storing unit based on the information on a printing positiondeviation amount of the print head among the density unevennessinformation acquired by the density unevenness information acquiringunit, and in which the N-valued data generating unit determines thegeneration ratios of the different sizes of dots for every predeterminedregion of the image data based on the two or more kinds of dot ratioinformation selected by the dot ratio information selecting unit, andperforms N-valued processing (M>N≧2) on the image data based on thedetermined generation ratios.

Thereby, similar to Aspect 9, in a case in which the banding phenomenonis caused in a plurality of places within one processing region, optimalprocessing according to the degree in each place can be performed.Therefore, it is possible to generate print data which can effectivelyeliminate the banding phenomenon or make the banding phenomenon nearlyinconspicuous while avoiding deterioration of image quality.

Aspect 38:

Further, according to Aspect 38 of the invention, there is provided animage processing program causing a computer to function as: an imagedata acquiring unit which acquires image data having M-value densityinformation (M≧3) for every pixel; a density unevenness informationacquiring unit which acquires information on the density unevenness ofthe nozzles which can print different sizes of dots; an N-valued datagenerating unit which performs N-valued processing (M>N≧2) on the imagedata acquired by the image data acquiring unit to generate N-valueddata; and a print data generating unit which generates print data fromthe N-valued data generated by the N-valued data generating unit. Here,the program causes the N-valued data generating unit to function todetermine the generation ratios of the different sizes of dots for everypredetermined region of the image data acquired by the image dataacquiring unit based on the density unevenness information acquired bythe density unevenness information acquiring unit, and to performN-valued processing (M>N≧2) on the image data based on the determinedgeneration ratios.

This, similar to Aspect 1, makes it possible to generate print datawhich effectively eliminate the banding phenomenon, such as a whitestreak or a dark streak, which is generated by the so-called flightdeflection or density unevenness, or make the banding phenomenon nearlyinconspicuous.

Further, it is possible to eliminate the banding phenomenon or make thebanding phenomenon nearly inconspicuous only in a portion where anydensity unevenness is being caused, by determining the proper generationfrequency of dots having each size for every nozzle according to densityunevenness, and changing the mixing ratio of dots with respect to thatwhen there is no density unevenness.

Further, similar to Aspect 29, since the above respective units can berealized using a general-purpose computer system, such as a personalcomputer (PC), the above respective units can be realized economicallyand easily compared with a case where the above respective units can berealized by making exclusive hardware (This is true of the followingaspect concerning an image processing program).

Aspect 39:

The image processing program of Aspect 39 is an image processing programaccording to Aspect 38 in which the information on the densityunevenness includes the information on a difference value between adensity value of a dot formed by each of the nozzles of the print headand an assumed density value.

Since this, similar to Aspect 2, allows different sizes of dots to bemore appropriately mixed in a printed image composed of a plurality ofdots, it is possible to generate print data which can effectivelyeliminate the banding phenomenon, such as a white streak or a darkstreak, which is generated by the so-called flight deflection or densityunevenness, or make the banding phenomenon nearly inconspicuous.

Aspect 40:

The image processing program of Aspect 40 is an image processing programaccording to Aspect 38 or 39, in which, if it is determined that thedifference value of the density value of the dot to be formed by each ofthe nozzles of the print head is greater than a predetermined thresholdbased on the information on the density unevenness, the N-valued datagenerating unit makes it greater than that when the generation ratio ofa large-sized dot is not determined.

Since this, similar to Aspect 3, allows different sizes of dots to bemore appropriately mixed in a printed image composed of a plurality ofdots, it is possible to generate print data which can effectivelyeliminate the banding phenomenon, such as a white streak or a darkstreak, which is generated by the so-called flight deflection or densityunevenness, or make the banding phenomenon nearly inconspicuous.

Aspect 41:

The image processing program of Aspect 41 is an image processing programaccording to Aspect 40 causing a computer to function as a densityunevenness correcting unit which corrects the density value of eachpixel of the image data acquired by the image data acquiring unit basedon the density unevenness information acquired by the density unevennessinformation acquiring unit. The N-valued data generating unit performsN-valued processing on the image data corrected by the densityunevenness correcting unit to generate N-valued data.

This, similar to Aspect 4, makes it possible to generate whicheffectively eliminate the banding phenomenon, such as a white streak ora dark streak, which is generated by the so-called flight deflection ordensity unevenness, or make the banding phenomenon nearly inconspicuous,and can also reduce deterioration of granularity.

Aspect 42:

The image processing program of Aspect 42 is an image processing programaccording to Aspect 40, causing a computer to function as a dot ratioinformation storing unit which stores dot ratio information whichspecifies the mixing ratios of the different sizes of dots, a dot ratioinformation selecting unit which selects a predetermined item of dotratio information among the dot ratio information stored in the dotratio information storing unit based on the density unevennessinformation acquired by the density unevenness information acquiringunit. Here, the N-valued data generating unit is adapted to determinethe generation ratios of the different sizes of dots for everypredetermined region of the image data acquired by the image dataacquiring unit based on the dot ratio information selected by the dotratio information selecting unit, and to perform N-valued processing(M>N>2) on the image data based on the determined generation ratios.

Since this, similar to Aspect 5, allows N-valued processing to beefficiently performed according to a generation ratio specified in theselected dot ratio information, it is possible to generate print datawhich more efficiently eliminate the banding phenomenon or make thebanding phenomenon nearly inconspicuous.

Aspect 43:

The image processing program of Aspect 43 is an image processing programaccording to Aspect 40, causing a computer to function as densityunevenness correcting unit which corrects the density value of eachpixel of the image data acquired by the image data acquiring unit basedon the density unevenness information acquired by the density unevennessinformation acquiring unit, a dot ratio information storing unit whichstores dot ratio information which specifies the mixing ratios of thedifferent sizes of dots, and a dot ratio information selecting unitwhich selects a predetermined item of dot ratio information among thedot ratio information stored in the dot ratio information storing unitbased on the density unevenness information acquired by the densityunevenness information acquiring unit. Here, the N-valued datagenerating unit determines the generation ratios of the different sizesof dots for every predetermined region of the image data corrected bythe density unevenness correcting unit based on the dot ratioinformation selected by the dot ratio information selecting unit, andperforms N-valued processing (M>N≧2) on the image data based on thedetermined generation ratios.

Since this, similar to Aspect 6, can effectively eliminate the bandingphenomenon, such as a white streak or a dark streak, which is generatedby the so-called flight deflection or density unevenness, or make thebanding phenomenon nearly inconspicuous, and can also reducedeterioration of granularity, a higher-quality printed material can beobtained. Further, since N-valued processing can be efficientlyperformed according to a generation ratio specified in the selected dotratio information, it is possible to generate print data which moreefficiently eliminate the banding phenomenon or make the bandingphenomenon nearly inconspicuous.

Aspect 44:

The image processing program of Aspect 44 is an image processing programaccording to Aspect 41 or 42, in which the dot ratio informationselecting unit selects a predetermined item of dot ratio informationfrom the dot ratio information stored in the dot ratio informationstoring unit for every plural nozzles including a target nozzle of theprint head, and nozzles in the vicinity of the target nozzle.

Since this, similar to Aspect 7, allows the generation ratio (dot mixingratio) to be determined in units of plural nozzles including a targetnozzle of a print head and about two to ten nozzles before and after thetarget nozzle, it is possible to generate print data which can moreeffectively eliminate the banding phenomenon resulting from the densityunevenness as well as the flight deflection or make the bandingphenomenon nearly inconspicuous.

Aspect 45:

The image processing program of Aspect 45 is an image processing programaccording to any one of Aspects 41 to 43, in which the dot ratioinformation selecting unit selects a predetermined item of dot ratioinformation among the dot ratio information stored in the dot ratioinformation storing unit based on the information on a printing positiondeviation amount of the print head among the density unevennessinformation acquired by the density unevenness information acquiringunit.

Since this, similar to Aspect 8, allows optimal processing to beperformed based on the flight deflection amount (the deviation amountfrom an assumed printing position), it is possible to generate printdata which effectively eliminate the banding phenomenon or make thebanding phenomenon nearly inconspicuous while avoiding deterioration ofimage quality.

Aspect 46:

The image processing program of Aspect 46 is an image processing programaccording to any one of Aspects 41 to 43, in which the dot ratioinformation selecting unit selects two or more kinds of dot ratioinformation among the dot ratio information stored in the dot ratioinformation storing unit based on the information on a printing positiondeviation amount of the print head among the density unevennessinformation acquired by the density unevenness information acquiringunit, and in which the N-valued data generating unit determines thegeneration ratios of the different sizes of dots for every predeterminedregion of the image data based on the two or more kinds of dot ratioinformation selected by the dot ratio information selecting unit, andperforms N-valued processing (M>N≧2) on the image data based on thedetermined generation ratios.

Thereby, similar to Aspect 9, in a case in which the banding phenomenonis caused in a plurality of places within one processing region, optimalprocessing according to the degree in each place can be performed.Therefore, it is possible to generate print data which can effectivelyeliminate the banding phenomenon or make the banding phenomenon nearlyinconspicuous while avoiding deterioration of image quality.

Aspect 47:

A computer-readable recording medium of Aspect 47 is a computer-readablerecording medium on which the image processing program according to anyone Aspects 38 to 46 is recorded.

This makes it possible to easily and certainly provide the imageprocessing program according to any one of Aspect 38 to 46 to consumers,such as users, by a computer-readable storage media, such as CD-ROMs,DVD-ROMs, FDs, and semiconductor chips.

Aspect 48:

Further, according Aspect 48 of the invention, there is provided animage processing method including: acquiring image data having M-valuedensity information (M≧3) for every pixel; acquiring the information onthe density unevenness of nozzles which can print different sizes ofdots; performing N-valued processing (M>N≧2) on the image data acquiredin the acquiring of the image data to generate N-valued data; andgenerating print data from the N-valued data generated in the generatingof the N-valued data. Here, in the generating of the N-valued data, thegeneration ratios of the different sizes of dots is determined for everypredetermined region of the image data acquired in the generating of theimage data based on the density unevenness information acquired in theacquiring of the density unevenness information, and N-value processing(M>N≧2) is performed on the image data based on the determinedgeneration ratios.

This, similar to Aspect 1, makes it possible to generate print datawhich effectively eliminate the banding phenomenon, such as a whitestreak or a dark streak, which is generated by the so-called flightdeflection or density unevenness, or make the banding phenomenon nearlyinconspicuous.

Further, it is possible to eliminate the banding phenomenon or make thebanding phenomenon nearly inconspicuous only in a portion where anydensity unevenness is being caused, by determining the proper generationfrequency of dots having each size for every nozzle according to densityunevenness, and changing the mixing ratio of dots with respect to thatwhen there is no density unevenness.

Aspect 49:

The image processing method of Aspect 49 is an image processing methodaccording to Aspect 48 in which the information on the densityunevenness includes the information on a difference value between adensity value of a dot formed by each of the nozzles of the print headand an assumed density value.

Since this, similar to Aspect 2, allows different sizes of dots to bemore appropriately mixed in a printed image composed of a plurality ofdots, it is possible to generate print data which can effectivelyeliminate the banding phenomenon, such as a white streak or a darkstreak, which is generated by the so-called flight deflection or densityunevenness, or make the banding phenomenon nearly inconspicuous.

Aspect 50:

The image processing method of Aspect 50 is an image processing methodaccording to 48 or 49 in which, if it is determined in the generating ofthe N-valued data that the difference value of the density value of thedot to be formed by each of the nozzles of the print head is greaterthan a predetermined threshold based on the information on the densityunevenness, it is made greater than that when the generation ratio oflarge-sized dots is not determined.

Since this, similar to Aspect 3, allows different sizes of dots to bemore appropriately mixed in a printed image composed of a plurality ofdots, it is possible to generate print data which can effectivelyeliminate the banding phenomenon, such as a white streak or a darkstreak, which is generated by the so-called flight deflection or densityunevenness, or make the banding phenomenon nearly inconspicuous.

Aspect 51:

The image processing method of Aspect 51 is an image processing methodaccording to Aspect 50, further including correcting the density valueof each pixel of the image data acquired in the acquiring of the imagedata based on the density unevenness information acquired in theacquiring of the density unevenness information. In the generating ofthe N-valued data, N-valued processing is performed on the image datacorrected in the correcting of the density unevenness to generateN-valued data.

This, similar to Aspect 4, makes it possible to generate whicheffectively eliminate the banding phenomenon, such as a white streak ora dark streak, which is generated by the so-called flight deflection ordensity unevenness, or make the banding phenomenon nearly inconspicuous,and can also reduce deterioration of granularity.

Aspect 52:

The image processing method of Aspect 52 is an image processing methodaccording to Aspect 50, further including storing dot ratio informationwhich specifies the mixing ratios of the different sizes of dots,selecting a predetermined item of dot ratio information among the dotratio information stored in the storing of the dot ratio informationbased on the density unevenness information acquired in the acquiring ofthe density unevenness information. Here, in the generating of theN-valued data, the generation ratios of the different sizes of dots isdetermined for every predetermined region of the image data acquired inthe acquiring of the image data based on the dot ratio informationselected in the selecting of the dot ratio information, and N-valuedprocessing (M>N≧2) is performed on the image data based on thedetermined generation ratios.

Since this, similar to Aspect 5, allows N-valued processing to beefficiently performed according to a generation ratio specified in theselected dot ratio information, it is possible to generate print datawhich more efficiently eliminate the banding phenomenon or make thebanding phenomenon nearly inconspicuous.

Aspect 53:

The image processing method of Aspect 53 is an image processing methodaccording to Aspect 50, correcting the density value of each pixel ofthe image data acquired in the acquiring of the image data based on thedensity unevenness information acquired in the acquiring of the densityunevenness information, storing dot ratio information which specifiesthe mixing ratios of the different sizes of dots, and selecting apredetermined item of dot ratio information among the dot ratioinformation stored in the storing of the dot ratio information based onthe density unevenness information acquired in the acquiring of thedensity unevenness information. Here, in the generating of the N-valueddata, the generation ratios of the different sizes of dots is determinedfor every predetermined region of the image data corrected in thecorrecting of the density unevenness based on the dot ratio informationselected in the selecting of the dot ratio information, and N-valuedprocessing (M>N≧2) is performed on the image data based on thedetermined generation ratios.

Since this, similar to Aspect 6, can effectively eliminate the bandingphenomenon, such as a white streak or a dark streak, which is generatedby the so-called flight deflection or density unevenness, or make thebanding phenomenon nearly inconspicuous, and can also reducedeterioration of granularity, a higher-quality printed material can beobtained. Further, since N-valued processing can be efficientlyperformed according to a generation ratio specified in the selected dotratio information, it is possible to generate print data which moreefficiently eliminate the banding phenomenon or make the bandingphenomenon nearly inconspicuous.

Aspect 54:

The image processing method of Aspect 54 is an image processing methodaccording to Aspect 51 or 52, in which, in the selecting of the dotratio information, a predetermined item of dot ratio information isselected from the dot ratio information stored in the storing of the dotratio information for every plural nozzles including a target nozzle ofthe print head, and nozzles in the vicinity of the target nozzle.

Since this, similar to Aspect 7, allows the generation ratio (dot mixingratio) to be determined in units of plural nozzles including a targetnozzle of a print head and about two to ten nozzles before and after thetarget nozzle, it is possible to generate print data which can moreeffectively eliminate the banding phenomenon resulting from the densityunevenness as well as the flight deflection or make the bandingphenomenon nearly inconspicuous.

Aspect 55:

The image processing method of Aspect 55 is an image processing methodaccording to any one of Aspects 51 to 53, in which, in the selecting ofthe dot ratio information, a predetermined item of dot ratio informationis selected from the dot ratio information stored in the storing of thedot ratio information based on the information on a printing positiondeviation amount of the print head among the density unevennessinformation acquired in the acquiring of the density unevennessinformation.

Since this, similar to Aspect 8, allows optimal processing to beperformed based on the flight deflection amount (the deviation amountfrom an assumed printing position), it is possible to generate printdata which effectively eliminate the banding phenomenon or make thebanding phenomenon nearly inconspicuous while avoiding deterioration ofimage quality.

Aspect 56:

The image processing method of Aspect 56 is an image processing methodaccording to any one of Aspects 51 to 53, in which, in the selecting ofthe dot ratio information, two or more kinds of dot ratio information isselected from the dot ratio information stored in the storing of the dotratio information based on the information on a printing positiondeviation amount of the print head among the density unevennessinformation acquired in the acquiring of the density unevennessinformation, and in which, in the generating of the N-valued data, thegeneration ratios of the different sizes of dots is determined for everypredetermined region of the image data based on the two or more kinds ofdot ratio information selected in the selecting of the dot ratioinformation, and N-valued processing (M>N≧2) is performed on the imagedata based on the determined generation ratios.

Thereby, similar to Aspect 9, in a case in which the banding phenomenonis caused in a plurality of places within one processing region, optimalprocessing according to the degree in each place can be performed.Therefore, it is possible to generate print data which can effectivelyeliminate the banding phenomenon or make the banding phenomenon nearlyinconspicuous while avoiding deterioration of image quality.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described with reference to the accompanyingdrawings, wherein like numbers reference like elements.

FIG. 1 is a functional block diagram showing a first embodiment of aprinting apparatus according to the invention.

FIG. 2 is a block diagram showing the hardware configuration of acomputer system which realizes the printing apparatus according to theinvention.

FIG. 3 is a partially enlarged bottom view showing the structure of aprint head according to the invention.

FIG. 4 is a partially enlarged side view showing the characteristics(flight deflection) of the print head according to the invention.

FIG. 5 is a conceptual diagram showing an example of a dot patternformed by the flight deflection phenomenon of one nozzle.

FIG. 6 is a conceptual diagram showing an example of an ideal dotpattern in which the flight deflection phenomenon is not caused.

FIG. 7 is a partially enlarged side view showing the characteristics(density unevenness) of the print head according to the invention.

FIG. 8 is an explanatory view showing the relationship between the inkdischarge amount of a print head, and dot size.

FIG. 9 is a conceptual diagram showing an example of a dot patternformed by a density unevenness phenomenon.

FIG. 10 is an explanatory view showing an example of the densityunevenness information acquisition processing by a density unevennessinformation acquiring unit.

FIG. 11 is an explanatory view showing an example of the densityunevenness correction processing by a density unevenness correctingunit.

FIGS. 12A to 12C are views showing an example of a dot conversion table.

FIGS. 13A to 13C are views showing another example of a dot conversiontable.

FIG. 14 is a view showing an example of a dither matrix used in N-valuedprocessing.

FIG. 15 is an explanatory view showing a dither method used in theN-valued processing.

FIGS. 16A and 16B are views showing an example of the relationshipbetween dot size and density.

FIGS. 17A and 17B are views showing another example of the relationshipbetween dot size and density.

FIG. 18 is a flowchart showing an example of the flow of the entireprinting processing of the invention.

FIG. 19 is a view showing an example of a combination of dot ratiotables.

FIG. 20 is a view showing another example of the combination of dotratio tables.

FIG. 21 is a conceptual diagram showing an example of an ideal dotpattern constituting a region to be processed, in which the flightdeflection phenomenon is not caused.

FIG. 22 is a conceptual diagram showing an example of a dot patternconstituting a region to be processed, in which the flight deflectionphenomenon is caused.

FIG. 23 is a conceptual diagram showing an example in which the densityunevenness correction processing has been performed to the dot patternof FIG. 22.

FIG. 24 is a conceptual diagram showing an example in which the dotmixing ratio has been changed along with the density unevennesscorrection processing to the dot pattern of FIG. 22.

FIG. 25 is a flowchart showing another example of the flow of the entireprinting processing of the invention.

FIGS. 26A to 26C are explanatory views showing differences in theprinting methods by the multipass type ink jet printer and the line-headtype ink jet printer.

FIG. 27 is a conceptual diagram showing another example of the structureof the print head.

FIG. 28 is a conceptual diagram showing an example of acomputer-readable recording medium on which a program according to theinvention is recorded.

FIG. 29 is a functional block diagram showing a second embodiment of theprinting apparatus according to the invention.

FIG. 30 is a flowchart showing an example of the flow of the processingrelated to a second embodiment.

FIG. 31 is a view showing an example of a dot pattern in which theflight deflection amount is great significantly, and generation of awhite streak cannot be avoided only by changing dot size.

FIG. 32 is a view showing an example of a dot pattern in which a speciallarge dot which is still larger than a typical large dot is printed.

FIG. 33 is a view showing an example of the density value of the speciallarge dot.

FIG. 34 is a view showing an example of dot ratio tables when thespecial large dot is used.

FIGS. 35A and 35B are views showing another example of a dot ratio tablein which dots are set with respect to the dot to be discharged greatly.

FIG. 36 is a view showing the relationship between the flight deflectionamount (the density fluctuation amount), and the use ratio of the dotratio tables 1 to 3 shown in FIGS. 12A to 12C.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

Hereinafter, embodiments of the invention will be described in detailwith reference to the accompanying drawings.

FIGS. 1 and 26 show a printing apparatus 100, a printing program, aprinting method, an image processing apparatus, an image processingprogram, an image processing method, and a computer-readable recordingmedium according to a first embodiment of the invention.

FIG. 1 is a functional block diagram showing the first embodiment of theprinting apparatus 100 according to the invention.

As shown in FIG. 1, the printing apparatus 100 includes a print head 200in which a plurality of nozzles which can print different sizes of dotsare arranged, an image data acquiring unit 10 which acquires image datahaving M-value density information (M≧3) for every pixel, a densityunevenness information acquiring unit 12 which acquires information onthe density unevenness of the nozzles of the print head 200, a densityunevenness correcting unit 14 which corrects the density value of eachpixel of the image data acquired by the image data acquiring unit 10based on the density unevenness information acquired by the densityunevenness information acquiring unit 12, a dot ratio informationstoring unit 16 which stores a plurality of dot ratio tables 300 whichspecifies the mixing ratio (dot generation ratio of each size) of eachof the different sizes of dots, a dot ratio information selecting unit18 which selects a predetermined dot ratio table among the dot ratiotables 300 stored in the dot ratio information storing unit 16, anN-valued data generating unit 20 which performs N-valued processing(M>N≧2) on the image data corrected by the density unevenness correctingunit 14 to generates N-valued data, a print data generating unit 22which generates print data from the N-valued data generated by theN-valued data generating unit 20, and an ink-jet type printing unit 24which performs printing using the print head 200 based on the print datagenerated by the print data generating unit 22.

First, the print head 200 will be described.

FIG. 3 is a partially enlarged bottom view showing the structure of theprint head 200, and FIG. 4 is a partially enlarged side view showing thestructure of the print head 200.

As shown in FIG. 3, the print head 200 has a long structure extending inthe width direction of a print sheet to be used for a so-calledline-head type printer, and is configured by integrally arranging thefollowing four nozzle modules 50, 52, 54, and 56 such that they arestacked in multiple stages in a printing direction (perpendicular to anozzle arrangement direction). The above four nozzles includes a blacknozzle module 50 in which a plurality of (eighteen in FIG. 3) nozzles Nwhich exclusively discharge black (K) ink are arranged linearly, ayellow nozzle module 52 in which a plurality of nozzles N whichexclusively discharge yellow (Y) ink are arranged linearly in the samedirection, a magenta nozzle module 54 in which a plurality of nozzles Nwhich exclusively discharge magenta (M) ink are arranged linearly in thesame direction, and a cyan nozzle module 56 in which a plurality ofnozzles N which exclusively discharge cyan (C) ink are arranged linearlyin the same direction. In addition, only black (K) ink may be used inthe case of a print head for the purpose of monochrome printing, and sixor seven colors of ink to which light magenta, light cyan, etc., areadded may be used in the case of a print head which targets ahigh-quality image.

FIG. 4 shows, for example, the black nozzle module 50 that is one of thefour nozzle modules 50, 52, 54, and 56 from the side (printingdirection), and shows a state (printing position deviation) where ink isdischarged in an oblique direction from a sixth nozzle N6 from the leftdue to the occurrence of a flight deflection phenomenon by the sixthnozzle N6 and thereby a dot is printed toward a dot which is dischargedby the adjacent normal nozzle N7.

Accordingly, when printing is performed using the black nozzle module50, as shown in FIG. 6, all dots are printed in their regular printingpositions in a state where the flight deflection does not occur (idealdot pattern). In contrast, as shown in FIG. 5, for example, if the sixthnozzle N6 from the left causes the flight deflection phenomenon, a dotmay be printed in a state where the dot printing position deviatestoward the adjacent normal nozzle N7 by a distance “a” from a desiredprinting position.

Further, in the print head 200 having such a structure, circular dotscan be printed on a white print sheet by discharging the inks suppliedinto ink chambers (not shown) which are provided in the nozzles N1, N2,N3, . . . respectively, from the nozzles N1, N2, . . . , and N3, . . .by piezoelectric elements, such as piezo actuators, which are providedin the ink chambers, respectively, and different sizes of dots can beprinted for each of the nozzles N1, N2, and N3, . . . by controlling thevoltages applied to the piezoelectric elements in multiple stages tocontrol the discharge amount of the ink from each ink chamber. Further,a voltage may be serially applied to a nozzle in two steps for a shorttime so that one dot may be formed by combining two discharges on aprint sheet. In this case, it is possible to discharge a large dotfollowing a small dot using a different discharge speed according to thesize of a dot to make ink reach almost the same position on the sheet toform one still larger dot. Printing which is performed for the purposeof realizing one dot is called one dot printing.

In the print head 200 having such a structure, a normal amount of inkmay not be discharged due to a variation in the size of the nozzle holesof the nozzles N1, N2, N3, . . . , and a difference in the supplypressure of ink during the manufacturing process in addition to theflight deflection phenomenon as described above.

For example, in the case of the print head 200, as shown in FIG. 3,irrespective of being controlled so that the nozzles N6 to N11 of acertain nozzle module may discharge the same ink discharge amount (thesame dot size), as shown in FIG. 7, the nozzle N7 may discharge a largeramount of ink than the discharge amount of a normal nozzle, such as thenozzle N6 (large discharge amount). In contrast, the nozzle N10 maydischarge a smaller amount of ink than the discharge amount of a normalnozzle (small discharge amount).

When a dot is printed using such a print head 200, in a nozzle having alarger amount of discharge than a specified value (large dischargeamount), the size of a dot to be printed may become greater than adesired dot size. In contrast, in a nozzle having a smaller amount ofdischarge than a specified value (small discharge amount), the size of adot to be printed may be smaller than a desired dot size. That is, forexample, as shown in FIG. 8, in a pattern in which eight different sizesof dots including “No Dot” are printed separately, a dot which is one ortwo sizes larger than the size of a dot formed by a normal nozzle isformed in a nozzle having a larger amount of discharge than the normalnozzle, and a dot which is one or two sizes smaller than the size of adot formed by a normal nozzle is formed in a nozzle having a smalleramount of discharge than the normal nozzle.

As a result, irrespective of the fact that the print head 200 iscontrolled to print a dot pattern with a uniform size as shown in FIG.6, a dot pattern as shown in FIG. 9 is printed, and a dot linecorresponding to the nozzle N7 becomes conspicuous as a dark streak, ora space appears in a dot line corresponding to the nozzle N10, andbecomes conspicuous as a white streak, which results in poor printingdue to the density unevenness.

In addition, although the dot pattern of FIG. 9 is formed using onlydots having one kind of size in order to make the explanation easy tounderstand, it is needless to say that troubles are caused even in a dotpattern in which dots having a plurality of sizes and dots having aplurality of colors are mixed like actual colors or actual monochromeprinted materials. Further, although an example in which a variation israndomly caused in the ink discharge amount is shown in FIG. 7 or FIG.9, in general, such a variation in ink discharge amount is easily causedin the nozzles located in the vicinity of an end or a central part of aprint head. Thus, there is a tendency that a prescribed amount or moreof ink is discharged from these nozzles in the vicinity of the end ofthe print head and thereby a prescribed size or more of dots areprinted, and a prescribed amount or less of ink is discharged from thenozzles in the vicinity of the central part of the line head and therebya prescribed size or less of dots are easily printed.

Further, although it is considered that the characteristics of such aprint head 200 may be fixed to some degree during the manufacturingprocess, a change after manufacture is relatively rare except for thepoor discharge caused by ink clogging, it is known that ink dischargeamount will differ for every nozzle due to various factors, such as achange in the viscosity of ink caused by deterioration with the lapse oftime, etc., a change in the diameter of nozzle holes, or a change in theoperation of piezoelectric elements. Further, as described above, theterm “dot” in the present embodiment is a base unit representingcharacters and figures of a printed material, and means a region whereink has reached a recording medium by one dot printing.

Next, the image data acquiring unit 10 is adapted to acquire M-valueimage data for printing sent from a printing instruction unit (notshown), such as a personal computer (PC) and a printer server, which isconnected with the printing apparatus 100, over a network etc., or toprovide a function which directly reads in and acquires image data froman image (data) reader, such as a scanner, a CD-ROM drive, etc. whichare not shown. Further, if the image data acquired is, for example,image data in which the gray-scale levels (density value) of each color(R, G, B) per pixel are expressed by 8 bits (0-255), the image dataacquiring unit is adapted to simultaneously exhibit a function whichperforms color conversion processing on the image data to convert theimage data into multi-valued CMYK data (in the case of four colors)corresponding to each ink of the print head 200.

Next, although the density unevenness information acquiring unit 12provides a function which acquires information on the density unevennessof the nozzles of such a print head 200, the information on “flightdeflection” of nozzles as described above in addition to the “densityunevenness” associated with poor ink discharge amount is also includedin this information on the density unevenness.

Specifically, this information on “density unevenness” includes at leastthe information on whether there is any nozzle which causes the flightdeflect phenomenon, or in a certain case, the information whichspecifies nozzles and indicates the amount of the flight deflection, inaddition to the information on whether there is any nozzle which causesdensity unevenness without printing a prescribed size of dots, and theinformation which specifies nozzles and indicates the degree of thedensity unevenness, all of which will be described in detail. Inaddition, the “information on density unevenness” acquired by thedensity unevenness information acquiring unit 12 is acquired andupdated, and is stored in an information storage section 12 a composedof a rewritable RAM, etc. so as to be readable, during manufacture ofthe printing apparatus 100 according to the invention or at anappropriate time after manufacture.

Next, the density unevenness correcting unit 14 is adapted to provide afunction which corrects the density value of each pixel of the imagedata acquired by the image data acquiring unit 10 particularly based onthe information on the “density unevenness” associated with poor inkdischarge amount among the density unevenness information acquired bythe density unevenness information acquiring unit 12.

For example, in a case in which the density value of each pixel of theimage data acquired by the image data acquiring unit 10 is expressed by8-bit 256 gray-scale levels, and irrespective of the fact that thedensity value of a certain pixel of the pixels is “210”, poor printingdischarge (“small” discharge amount) of a nozzle corresponding to thepixel allows printing of only a dot whose size to be actually printed bythe nozzle is equivalent to a density value “126,” the density value ofthe pixel is corrected to a higher value so that a dot having a normalsize corresponding to an original density value may be printed. Incontrast, in a case in which the density value of each pixel of theimage data acquired by the image data acquiring unit 10 is expressed by8-bit 256 gray-scale levels, and irrespective of the fact that thedensity value of a certain pixel of the pixels is “126”, poor printingdischarge (“large” discharge amount) of a nozzle corresponding to thepixel allows printing of a dot whose size to be actually printed by thenozzle is equivalent to a density value “256,” the density value of thepixel is corrected to a lower value so that a dot having a normal sizecorresponding to an original density value may be printed.

FIGS. 10 and 11 show an example of the density unevenness correctionprocessing by the density unevenness correcting unit 14, and the densityunevenness information acquisition processing by the density unevennessinformation acquiring unit 12.

Specifically, as for the density unevenness information acquisitionprocessing by the density unevenness information acquiring unit 12, forexample, as shown in FIG. 10, several kinds of density patches (densitydata) having different densities are used, this density patch is thenactually printed on a printing medium using the above-mentioned printhead 200, and the degree of the density unevenness for every nozzle isthen measured by reading the printing result using an optical densityreader, such as a scanner, so that the density unevenness informationcan be acquired. Also, as for the density unevenness correctionprocessing by the density unevenness correcting unit 14, the correctiondata for every nozzle is prepared based on the density unevennessinformation, and the density value of each pixel of the image dataacquired by the image data acquiring unit is then adjusted based on thecorrection data so that density unevenness can be corrected.

Next, the dot ratio information storing unit 16 is adapted to provide afunction which stores (preserves) a plurality of dot ratio tables 300(dot ratio tables 1, 2, 3, . . . ) which specify the mixing ratio ofeach of the different sizes of dots according to the density value ofthe image data. Specifically, electronic information is recorded onelectromagnetic recording media, such as auxiliary memories (storages),such as RAMs (main storages) and HDDs (hard disk drives) of a computersystem so that it can be read out freely.

FIGS. 12A to 12C show examples of the dot ratio tables 300,respectively.

As shown in these figures, each of these dot ratio tables 300 shows therelationship (mixing ratio) between the generation ratio (y-axis) of twokinds of dots including a “small dot (Sdot)” and a “large dot (Ldot)”and the density (x-axis). Specifically, each dot ratio table specifiesthat, based on the average density of pixels in a region to beprocessed, “small dots” are preferentially generated when the averagedensity is low, and as the average density rises, the generation ratioof “small dots” becomes low and the generation ratio of “large dots”becomes high.

First, the dot ratio table 300 shown in FIG. 12A specifies obtaining animage with graininess, i.e., a feeling of roughness, is minimized byutilizing the “small dots (Sdot)” to the maximum.

That is, in the dot ratio table 300 of FIG. 12A, when the averagedensities of the pixels in a region to be processed are A and B, only“small dots” are generated, and when the average density in the vicinityof a portion where the average density exceeds near “125 (8 bits, 256gray-scale levels)” is C, “large dots” are generated along with “smalldots” so as to express the density of the region.

Meanwhile, the dot ratio table 300 of FIG. 12B is a table whichspecifies dot mixing ratios in a case in which banding is caused in aregion to be processed. That is, in the dot ratio table 300 shown inFIG. 12B, when the average density of the pixels in a region to beprocessed is A, only “small dots” are generated similarly to the dotratio table 300 of FIG. 12A. However, when the average density is B,“large dots” already begin to be generated, and when the average densityis C, the generation ratio of large dots becomes almost the same as thatof “small dots” so as to express the density of the region.

Moreover, the dot ratio table 300 of FIG. 12C is a table which specifiesdot mixing ratios in a case in which greater banding is caused in aregion to be processed.

Moreover, in the dot ratio table 300 of FIG. 12C, when the averagedensities of the pixels in a region to be processed are A and B, “smalldots” and “large dots” are simultaneously generated in the samegeneration ratio to express the density of the region. However, when theaverage density of the pixels in a region to be processed is C, thegeneration ratio of “large dots” becomes higher than that of “smalldots,” so as to express the density of the region. Although the feelingof roughness increases with a shift from FIG. 12B toward FIG. 12C, it iseasy to avoid characteristics inherent in nozzles, such as densityunevenness and banding, because large dots are easily generated.

Here, as for a method of determining the region of the image data to beprocessed, the region is not particularly limited as long as it includesa dot generated by a nozzle which causes density unevenness and flightdeflection, and may be a unit of 2 to 10 pixels including the problemnozzle and nozzles before and after the problem nozzle. For example, theregion may be only a target nozzle, or as shown in FIG. 14, it may be aunit (region) of about 4×4 (pixel) size (substantially four lines), andmay be a unit (region) greater than that size.

Next, the dot ratio information selecting unit 18 is adapted to providea function which selects a predetermined dot ratio table 300 among theplurality of dot ratio tables 300 stored in the dot ratio informationstoring unit 16 based on the density unevenness information acquired bythe density unevenness information acquiring unit 12.

Here, although a criterion for the selection of the dot ratio tables 300by the dot ratio information selecting unit 18 is not particularlylimited, for example, one or two kinds of combinations are used based ondensity unevenness information, such as a correction amount of densityunevenness and flight deflection amount, or a dot ratio table 300optimal for every nozzle is selected and used. Concrete examples thereofwill be described below in detail.

Next, although the N-valued data generating unit 20 is adapted toprovide as its fundamental function a function which performs N-valuedprocessing (N≧2) to each pixel of the image data corrected by thedensity unevenness correcting unit 14 to generate N-valued image databased on a typical binarization processing method which is generallyused in the field of image processing, such as a “dither method”, theN-valued data generating unit 20 is adapted to perform N-valuedprocessing (M>N≧2) on the image data corrected by the density unevennesscorrecting unit 14 so that it may become a dot mixing ratio specified ina dot ratio table 300 selected by the dot ratio information selectingunit 18.

FIG. 14 shows an example of a dither matrix (dither table) 400 used inthe binarization performed by the N-valued data generating unit 20. Asshown in this figure, each grid of the dither matrix 400 corresponds toeach pixel of the image data to be processed, and as shown in FIG. 15,binarization processing of the multi-valued image data is performed bycomparing the density value of each pixel of the image data with thenumerical value (threshold) of each grid of the dither matrix 400, andperforming binarization determination (ON/OFF of a dot) that, if thevalue of a gray image is greater than the numerical value, black isselected (dotting) and, if the value of the gray image is smaller thanthe numerical value, white is selected (non-dotting).

Furthermore, when the above-mentioned dot ratio tables 300 are selectedfor every nozzle of the print head 200 in such fundamental binarizationprocessing, the N-valued data generating unit 20 is adapted to performN-valued processing for every processing region so that it may become adot mixing ratio specified in the dot ratio tables 300.

Therefore, this N-valued data generating unit 20 converts a densityvalue using a dot ratio table 300 selected by the dot ratio informationselecting unit 18, and compares the value with the dither matrix 400.

Specifically, L_val=L_Conv (pixel density) and S_val=S_Conv (pixeldensity) are performed for every pixel. Here, the L_Conv means thegeneration frequency of the large dots (Ldot) in the dot ratio tables300. For example, in a case in which the dot ratio table 300 of FIG. 12Ais used, the L_Conv always becomes “0” in an input density of “0” to“127” and the L_Conv becomes a value which rises linearly from “0” to“128” in an input density of “127” to “255.” Meanwhile, the S_Conv meansthe generation frequency of the small dots (Sdot). Similarly, in a casein which the dot ratio table 300 of FIG. 12A is used, the S_Conv becomesa function which rises linearly from “0” to “127” in an input density of“0” to “127.” However, since threshold processing is performed even ifthe same dither matrix 400 as the dither matrix 400 used for the largedots is used, a situation occurs that a small dot is not printed in theposition which a large dot has been generated, even if a small dot isset to ON. Thus, the dot mixing ratio of the dot ratio tables 300 can bekept by outputting to S_Conv a value obtained by summing up thegeneration ratio of small dots and the generation ratio of large dots.

In addition, in a case in which the maximum printing amount of dots isset to “128” and the density maximum value is set to “255” in performingconversion based on the generation ratio from density, the consistencyof data can be maintained by doubling a converted value based on the dotratio tables 300 from the density.

Next, the print data generating unit 22 provides a function which sets acorresponding dot for every pixel of the N-valued data to which N-valuedprocessing has been performed to generate the data for printing whichcan be used in the ink-jet type printing unit 24 by the N-valued datagenerating unit 20.

FIGS. 16A and 16B show an example of the density value and the dot size.

For example, referring FIG. 16A, the average densities “84”, “168”, and“255” can be expressed by allocating a “small dot,” a “middle dot,” anda “large dot” to pixels, respectively, and referring to FIG. 16B, theaverage densities “128” and “255” can be expressed by a “small dot” anda “large dot” to pixels, respectively. In addition, in the followingembodiment, as shown in FIG. 16B, an example using two kinds of dots,such as a “small dot” and a “large dot, ” in order to make theexplanation easy to understand will be described.

Further, the technique itself which prints separate sizes of dots in anydirection in one printed material as described above is a conventionallyknown technique, and a technique which has conventionally beenfrequently used under the name called MSDT (Multi Size Dot Technology)particularly when a printed material which realizes printing speed andprinted image quality with high balance.

That is, making the dot size small ensures high image quality, whereasmaking the dot size small requires advanced performance of machineaccuracy, and forming a Beta image with small dots needs a lot of dotsto be printed. A high-definition image portion is obtained by making thedot size small, and a Beta image portion is obtained by realizingprinting speed and image quality with high balance by using thetechnique of printing separate sizes of dots, including making the dotsize large.

In addition, as the technical method of realizing printing of separatesizes of dots as such, for example, in the case of the method in which apiezoelectric element (piezo actuator) is used in the print head 200 asdescribed above, it is possible to easily realize the separate sizes ofdots by changing the voltage to be applied to the piezoelectric elementto control the discharge amount of ink.

Next, the printing unit 24 is an ink-jet type printer which is adaptedto inject ink in the form of dots from the nozzle modules 50, 52, 54,and 56 formed in the print head 200 while one or both of the printingmedium (sheet) S and the print head 200 moves so that a predeterminedimage composed of a large number of dots may be formed on the printingmedium S. This printing unit is composed of known components, such as aprint head feeding mechanism (not shown) which reciprocates the printhead 200 above the printing medium S in the width direction thereof (inthe case of a multipass type printer), a sheet feeding mechanism (notshown) which moves the printing medium S, and a print controllermechanism (not shown) which controls the discharge of ink of the printhead 200 based on the data for printing, in addition to theabove-mentioned print head 200.

Here, the printing apparatus 100 includes a computer system forrealizing on software various kinds of controls for printing, and theimage data acquiring unit 10, the density unevenness informationacquiring unit 12, the density unevenness correcting unit 14, the dotratio information storing unit 16, the dot ratio information selectingunit 18, the N-valued data generating unit 20, the print data generatingunit 22, the printing unit 24, etc. The hardware configuration of theprinting apparatus, as shown in FIG. 2, is obtained by connecting a CPU(Central Processing Unit) 60 that is a central processing unit which isresponsible for various kinds of control and arithmetic processing, aRAM (Random Access Memory) 62 which constitutes a main storage, a ROM(Read-Only Memory) 64 that is a read-only storage, by various internaland external buses 68 including a PCI (Peripheral ComponentInterconnect) bus, an ISA (Industrial Standard Architecture) bus, etc.,and by connecting the network L for communicating with an externalstorage (Secondary Storage) 70, such as an HDD (Hard Disk Drive), aprinting unit 24, an output device 72, such a CRT or an LCD monitor,input devices 74, such as a console panel, a mouse, a keyboard, and ascanner, a printing instruction unit (not shown), etc. to the buses 68via an input/output interface (I/F) 66.

When power is supplied, a system program, such as BIOS, which is storedin the ROM 64, loads to the RAM 62 various kinds of exclusive computerprograms stored in advance in the ROM 64 or various kinds of exclusivecomputer programs installed in the storage 70 via storage media, such asCD-ROM, DVD-ROM, and a flexible disk (FD), or via the communicationnetwork L, such as the Internet, and the CPU 60 performs predeterminedcontrol and arithmetic processing by using various resources accordingto the commands described in the programs loaded to the RAM 62 so thateach function of each unit as described above can be realized onsoftware.

Next, an example of print processing using the printing apparatus 100will be described mainly referring to the flowchart of FIG. 18.

In addition, although the print head 200 for printing dots as describedabove can generally print dots of a plurality of colors, such as fourcolors and six colors, at about the same time, a case in which any dotis printed by the print head 200 for any one color (monochrome ormonochrome image) will be described in the following examples in orderto make the explanation easy to understand.

First, if the printing apparatus 100 has completed a predeterminedinitial operation for print processing after supply of power thereto andis connected with a printing instruction terminal (not shown), such as apersonal computer, the image data acquiring unit 10 monitors whetherthere is any explicit printing instruction from the printing instructionterminal in the first step S100, and, if it is determined that thisprinting instruction and the multi-valued image data to be processedhave been sent, the image data acquiring unit acquires the image data inthe next step S102.

In addition, when the image data acquired by the image data acquiringunit 10 at this time is multi-valued RGB data, as described above, thisdata is converted into multi-valued CMYK data corresponding to used ink,etc. based on a predetermined conversion algorithm, and thereafter themulti-valued CMYK data will be treated as the image data to beprocessed.

Next, if the image data to be processed is acquired in this way, theprocess proceeds to the next step S104 where the density unevennessinformation on the print head 200 which is stored in the informationstorage section 12 a of the density unevenness information acquiringunit 12, etc., is acquired. Thereafter, the process proceeds to the nextdetermination step S106 where it is determined whether or not any nozzlewhich causes the “density unevenness” due to poor ink discharge amountexists in the print head 200.

The process jump to Step S110 when it is determined that the “densityunevenness” does not exists (density unevenness is not caused) (No).However, when it is determined that any nozzle which causes the “densityunevenness” exists (Yes), the process proceeds directly to the next stepS108 where the density value of a pixel (row) corresponding to thenozzle which causes the “density unevenness” is corrected. Specifically,for example, as described above, in a case in which the printing densityof a nozzle which causes the “density unevenness” is smaller than aspecified value (in a case in which the ink discharge amount becomesless than a prescribed amount, and consequently the size of a dot to beprinted becomes small), correction is caused to the density value of apixel (row) corresponding to the nozzle may be increased so that theprinting density of the nozzle may become a specified value. This caneffectively eliminate the banding phenomenon resulting from “densityunevenness” or can make the phenomenon nearly inconspicuous.

Next, if the correction processing of a density value is completed inthis way, the process proceeds to the determination step S110 where itis determined whether or not there exist any nozzle which causes thephenomenon of a predetermined amount or more of flight deflection whichmay cause a banding phenomenon among the nozzles of the print head 200based on the density unevenness information acquired in the step S104.

When it is determined that there exists no nozzle which causes theflight deflection phenomenon (No), the process proceeds to the step S116where typical N-valued-data generation processing is performed for everypredetermined region to be processed by the dither method as describedabove. In contrast, if it is determined that there exists any nozzlewhich causes the flight deflection phenomenon (Yes), the processproceeds to the next step S112 where a dot ratio table 300 according tothe flight deflection amount is selected.

FIGS. 19 and 20 show an example of a selection criterion and a selectingmethod of the dot ratio tables 300 in the step S112.

The selection criterion of the dot ratio tables 300 of FIG. 19 isselected by combining three kinds of dot ratio tables 300 (specifically,FIG. 12A to FIG. 12C are referred to as Table 1, Table 2, and Table 3,respectively) according to the flight deflection amount (correspondingto the density fluctuation amount which shows the size of densityunevenness). Specifically, “Table 1” is selected when the flightdeflection amount is smaller than a first threshold, “Table 3” isselected when the flight deflection amount is greater than a secondthreshold, and “Table 2” is selected when the flight deflection amountis located between the first threshold and the second threshold.

Meanwhile, the dot ratio table selecting method of FIG. 20 specifiesthat the dot ratio tables 300 selected as the flight deflection amountfor every nozzle is selected.

If a predetermined dot ratio table 300 is selected in this way, theprocess proceeds to the next step S114 where N-valued processing isperformed for every predetermined region of the image data so that itmay become a dot ratio specified in the dot ratio table 300. Thereafter,the process proceeds to the next step S118 where the print data that adot corresponding to the N-valued processing is allocated to everypredetermined region is generated. Then, in the final step S120,printing is performed based on the print data by using the print head200, and the processing is ended.

FIG. 21 shows an example of an ideal dot pattern in which neither the“density unevenness” nor the “flight deflection” are caused, in eachprocessing object region of a printed material to which the printingprocessing has been performed in this way, and FIG. 22 shows an exampleof a dot pattern in which the “flight deflection” is caused in somenozzles and consequently the dots to be printed by the nozzles areprinted in a state where they deviate by a distance “a” from theirregular position in the same printed material.

Also, FIG. 23 shows that the density unevenness correction processinghas been performed to a pixel row corresponding to a nozzle which causesprinting deviation in a case in which the “flight deflection” as shownin FIG. 22 is caused. Simply performing the density unevennesscorrection processing to the pixel row in which a white streak isgenerated as such makes the dot density high and makes the white streakstill remain in that part. As a result, not only the banding resultingfrom the flight deflection cannot be eliminated, but also the density ofthe pixel row becomes rather high, and consequently a dark streak in thevicinity of the white streak will be more conspicuous.

In contrast, FIG. 24 shows that the dot mixing ratio of the processingregion is changed according to the dot ratio tables 300 in a case inwhich the flight deflection is caused as described above. Although thisdeteriorates the granularity of that part slightly, a white streakresulting from the banding can be effectively eliminated or made nearlyinconspicuous.

Further, since the dot mixing ratio is changed based on the averagedensity value of the processing region, the area gray-scale inherent inthe processing region is similarly not spoiled.

In this way, according to the invention, different sizes of dots can bemade appropriately mixed in a printed image composed of a plurality ofdots based on the dot ratio tables 300. Therefore, it is possible toeffectively eliminate the banding phenomenon, such as a white streak ora dark streak, which is generated by the so-called flight deflection ordensity unevenness, or make the banding phenomenon nearly inconspicuous.As a result, a high-quality printed material can be obtained easily.

In addition, although the dot pattern shown in FIG. 24 in which the dotmixing ratio has been changed is obtained by changing the dot mixingratio according to the dot ratio tables 300 which specify the mixingratio of dots having two kinds of different sizes as shown in FIGS. 12Ato 12C, etc., the dot ratio tables 300 which specify the mixing ratio ofdots having three kinds of different sizes as shown in the dot ratiotables 300 of FIG. 13C, etc. may be used. In this case, the density ofthe processing region will be expressed by the combination of the dotshaving three kinds of different sizes.

Further, although the present embodiment describes that theexistence/nonexistence (Step S110) of the flight deflection phenomenonand the existence/nonexistence determination (Step S106) of the densityunevenness are determined separately, it is also possible to considerthat the occurrence of the density unevenness phenomenon itself iscaused by the flight deflection phenomenon, and vice versa.

Accordingly, the selection processing, etc. of the dot ratio tables 300as shown in Step S112, etc. may be performed based on either the densityunevenness or the flight deflection phenomenon.

Specifically, for example, as shown in the flow chart of FIG. 25, whenit is determined that there is no density unevenness in thedetermination processing about the existence/nonexistence of the densityunevenness in the fourth step S106 (No), the process proceeds straightto Step S116 where the typical N-valued data generation processing isperformed. In contrast, when it is determined that there is any densityunevenness in the determination processing about theexistence/nonexistence of the density unevenness in this step S106(Yes), the same density value correction processing as the above isperformed in the next step S108, and thereafter the process proceedsstraight to the next step S112 where a dot ratio table 300 is selectedaccording to the density value correction amount, skipping thedetermination step S110 about the existence/nonexistence of the flightdeflection phenomenon as shown in Step S110 of the flow chart of FIG.18.

An aspect which does not use the information on the above-mentionedflight deflection phenomenon for the trigger which performs theselection processing of the dot ratio tables 300 in this way may beused. In addition, in a case in which only the density unevennessinformation is used and the information on the flight deflectionphenomenon is not used in the selection processing of the dot ratiotables 300 like this, as shown in FIG. 1, the information acquired fromthe density unevenness information acquiring unit 12 by the dot ratioinformation selecting unit 18 is only the information on the densityunevenness. Therefore, it is possible to significantly reduce the amountof information. Accordingly, it is possible to obtain the effect thatthe time taken to acquire the information or the time taken to processthe information cam be significantly reduced.

Further, the print head 200 in the present embodiment corresponds to theprint head in the printing apparatus of Aspect 1. Similarly, the imagedata acquiring unit 10, the density unevenness information acquiringunit 12, the density unevenness correcting unit 14, the dot ratioinformation storing unit 16, the dot ratio tables, the dot ratioinformation selecting unit 18, N-valued data generating unit 20, theprint data generating unit 22, the printing unit 24, etc., correspond tothe image data acquiring unit the density unevenness informationacquiring unit, the density unevenness correcting unit, the dot ratioinformation storing unit, the dot ratio information, the dot ratioinformation selecting unit, the N-valued data generating unit, the printdata generating unit, the printing unit, etc., respectively, in theprinting apparatus of Aspect 6, etc.

Further, since the printing apparatus 100, etc. of the invention whichis realized in the above embodiment, is adapted such that the dot mixingratio is changed according to the density unevenness information of theprint head, without making substantial alterations to the existing printhead 200 and existing printing unit 24 themselves, it is not necessaryto particularly prepare exclusive ones as the print head 200 or theprinting unit 24 and it is possible to utilize a conventional existingink-jet type print head 200 and existing ink-jet type printing unit 24(printer).

Accordingly, if the print head 200 and the printing unit 24 areseparated from the printing apparatus 100 of the invention, theirfunctions can be realized only with a general-purpose informationprocessor (image processing apparatus), such as a personal computer.

Further, not to mention that the printing apparatus 100 of the inventionis not limited to the aspect in which all the functions are accommodatedinto the housing as one, for example, some of the functions may bepartitioned so that the functions from the image data acquiring unit 10to the N-valued data generating unit 20 may be realized on the side of apersonal computer, and the functions of the print data generating unit22 and the printing unit 24 may be realized on the side of a printer.

Further, the invention can be similarly applied to a case where thedischarge direction of ink is perpendicular (normal) but the positionwhere a nozzle is formed deviates from a regular position, andconsequently a dot to be formed experiences the same results as theflight deflection phenomenon, as well as the density unevenness and theflight deflection phenomenon.

Furthermore, the invention can also be similarly applied to a case inwhich ink is not discharged from a specific nozzle due to ink clogging,etc.

Further, the printing apparatus 100 of the invention can be applied notonly to a line-head type ink jet printer but also to a multipass typeink jet printer (serial printer). If the printing apparatus is aline-head type ink jet printer, it is possible to obtain at one pass ahigh-quality printed material in which a white streak and a dark streakare hardly conspicuous, and if the printing apparatus is a multipasstype ink jet printer, it is possible to realize printing at a higherspeed than before because the number reciprocations can be reduced. Forexample, in a case in which desired image quality can be realized by oneprinting, as compared with a case where printing is performed byreciprocal printing of K times, printing time can be shortened to 1/K.

FIGS. 26A to 26C respectively show the printing methods by the multipasstype ink jet printer and the line head type ink jet printer.

As shown in FIG. 26A, in a case in which the image data to be printed ona rectangular print sheet S is targeted, the print head 200 in theline-head type ink jet printer, as shown in FIG. 26B, has a lengthequivalent to the width of the print sheet S, and this print head 200 isfixed and the print sheet S is caused to move in a directionperpendicular to the nozzle arrangement direction with respect to thisprint head 200, thereby completing so-called one scanning (one pass). Inaddition, it is also possible to perform printing while the print sheetS is fixed and the print head 200 is caused to move in a directionperpendicular to the nozzle arrangement direction or both the printsheet and the print head are caused to move in opposite directions, likea so-called flat-bed type printer. In contrast, the multipass type inkjet printer, as shown in FIG. 26C, is adapted to perform printing bylocating a print head 200 which is far shorter than the sheet width in adirection perpendicular to the nozzle arrangement direction, and movingthe printing sheet S by a predetermined pitch in a directionperpendicular to the nozzle arrangement direction while the print headis caused to reciprocate several times in the nozzle arrangementdirection. Accordingly, the latter multipass type ink jet printer(serial printer) has a drawback that printing time is longer as comparedwith the former line-head type ink jet printer, while it has anadvantage that, since the print head 200 can be repeatedly located in anarbitrary spot, it is possible to reduce the above-mentioned whitestreak phenomenon to some degree, among the banding phenomena asmentioned above.

Further, although the ink jet printer which discharges in the form ofdots to perform printing has been described as an example in the presentembodiment, the invention can also be applied to other printingapparatuses using a print head of the type in which a printing mechanismis arranged in a line, for example, a thermal head printer also called athermal transfer printer, a thermosensitive printer, and the like.

Further, FIG. 3 shows that each of the nozzle modules 50, 52, 54, and 56provided for each color of the print head 200 is configured such thatthe nozzles N are arranged continuously in the longitudinal direction ofthe print head 200. However, as shown in FIG. 27, each of the nozzlemodules 50, 52, 54, and 56 may be composed of a plurality of shortnozzle units 50 a, 50 b, . . . , and 50 n, and these nozzle units may bearranged backward and forward in the direction of movement of the printhead 200. Particularly if each of the nozzle modules 50, 52, 54, and 56is composed of the plurality of short nozzle units 50 a, 50 b, . . . ,and 50 n like this, the yield rate improves significantly compared withthe case where each nozzle module is composed of a long nozzle unit.

Further, each mechanism for realizing the printing apparatus 100 of theabove-mentioned present embodiment can be realized in software using acomputer system incorporated into most existing printing apparatuses. Acomputer program is incorporated into a product in the state of beingstored in a semiconductor ROM in advance, or is distributed vianetworks, such as the Internet. Otherwise, as shown in FIG. 28, thecomputer program can be easily provided to a desired user via acomputer-readable recording media R, such as CD-ROMs, DVD-ROMs, and FDs.

Next, FIGS. 29 and 30 show a printing apparatus 100, a printing program,a printing method, an image processing apparatus, an image processingprogram, an image processing method, and a computer-readable recordingmedium according to a second embodiment of the invention.

First, FIG. 29 is a functional block diagram showing a printingapparatus 100 according to the second embodiment of the invention.

As shown in FIG. 29, the printing apparatus 100 mainly includes a printhead 200 in which a plurality of nozzles which can print different sizesof dots are arranged, an image data acquiring unit 10 which acquiresimage data having M-value density information (M≧3) for every pixel, adensity unevenness information acquiring unit 12 which acquiresinformation on the density unevenness of the nozzles of the print head200, a dot ratio information storing unit 16 which stores a plurality ofdot ratio tables 300 which specifies the mixing ratio (dot generationratio of each size) of each of the different sizes of dots, a dot ratioinformation selecting unit 18 which selects a predetermined dot ratiotable 300 among the dot ratio tables 300 stored in the dot ratioinformation storing unit 16, an N-valued data generating unit 20 whichperforms N-valued processing (M>N≧2) on the image data to generatesN-valued data, a print data generating unit 22 which generates printdata from the N-valued data generated by the N-valued data generatingunit 20, and an ink-jet type printing unit 24 which performs printingusing the print head 200 based on the print data generated by the printdata generating unit 22.

That is, the present embodiment has a configuration from which thedensity unevenness correcting unit 14 in the above first embodiment isomitted, and shows an example of printing processing which isparticularly effective for the printing apparatus 100 including a printhead 200 which hardly causes density unevenness phenomenon, but causesthe flight deflection phenomenon.

Accordingly, although the printing processing related to the presentembodiment is the same as that of the above first embodiment from thefirst step S100 to the third step S104 as shown in FIG. 30, thedetermination processing on whether or not any flight deflection existsis performed in the next step S110, and the same processing as that ofthe above first embodiment is then performed according to thedetermination result.

Since this makes it unnecessary to perform the correction processing,etc. to the density unevenness, the banding elimination processing canbe realized more efficiently.

Further, the print head 200 in the present embodiment corresponds to theprint head in the printing apparatus of Aspect 1. Similarly, the imagedata acquiring unit 10, the density unevenness information acquiringunit 12, the dot ratio information storing unit 16, the dot ratiotables, the dot ratio information selecting unit 18, N-valued datagenerating unit 20, the print data generating unit 22, the printing unit24, etc., correspond to the image data acquiring unit the densityunevenness information acquiring unit, the density unevenness correctingunit, the dot ratio information storing unit, the dot ratio tables, thedot ratio information selecting unit, the N-valued data generating unit,the print data generating unit, the printing unit, etc., respectively,in the printing apparatus of Aspect 4, etc.

In addition, although the first and second embodiments have only beendescribed in conjunction with the case in which the same kind of dotratio fluctuates in density, it is possible to set the dot ratio so thata special size of dots may be generated only under specific conditions.This is because generation of a white streak cannot be avoidedparticularly in a dot size which is generally designed in nozzles havinga large amount of flight deflection.

FIG. 31 is a view showing an example of a dot pattern in which theflight deflection amount is significantly great, and generation of awhite streak cannot be avoided only by changing dot size.

In contrast, FIG. 32 shows that a special large dot which is stilllarger than a typical large dot is printed. It can be understood fromthis figure that it is possible to make a white streak inconspicuous byprinting such a special large dot. Further, in a case of a Beta imagewhose entire surface is coated with ink, when attention is paid to anozzle location where the flight deflection amount is great, it ispossible to address such a problem by using such a large dot, though theimage cannot be coated with typical dots.

FIG. 33 is an example showing the density value of such a special largedot. The dot which realizes density which is not usually needed is givenlike this. Further, FIG. 34 is a view showing an example of dot ratiotables 300 when such a special large dot is used. It can be understoodfrom this figure that, even if very great banding is caused by applyingsuch a significantly large dot, visual banding can be effectivelyeliminated. In addition, although the dot ratio table shown in FIG. 34is seen as if being composed of two graphs because both the generationratio of S dot and the generation ratio of L dot are set to the sameratio and thus both graphs overlap each other completely, it ispractically composed of three graphs corresponding to S dot, L dot, andSL dot, respectively.

Further, although it is assumed in each of the above-mentionedembodiments that the density to be output is set to be always the sameeven if the mixing ratio of dots is changed with respect to the densityindicated by N-valued processing, and the module which corrects thedensity unevenness is separately prepared and processed in a case inwhich density fluctuation is required due to a difference between dotsizes like the above embodiments, the density unevenness can be causedto be mixed in advance in the dot ratio tables 300 as anotherembodiment.

That is, if the dot ratio tables 300 in which the dot size is taken intoconsideration with respect to the nozzles which tends to increase in dotsize as a whole is set and processed, it is possible to absorb all thevariations of the nozzles by selecting only the dot ratio tables 300.

For example, as shown in FIG. 20, a dot ratio table 300 to be used forevery nozzle is set in advance, and processing is performed while thedot ratio table 300 set for every nozzle is selected during printing.

As shown in FIGS. 17A and 17B, FIGS. 35A and 35B show examples of thedot ratio tables 300 to be set for the dot greatly discharged, andcorrespond to the dot ratio tables 300 of FIGS. 12A to 12C of FIG. 16Bmentioned above, respectively. In FIGS. 35A and 35B, the dot printingamount in each density is reduced as much as an increase in dot sizewithout changing the range to be covered by a dot of each size.

Further, in a case in which changing a density axis also taken intoconsideration and processing is performed by this method, the resultbecomes the same as the case where the density change and the dot ratiotables 300 are unified together, and the dot ratio tables in this caseare as shown in FIGS. 13A and 13B.

In addition, similarly to FIGS. 12A and 12B, the dot ratio table 300 ofFIG. 13A specifies that only “small dots” are generated when the averagedensity of a region to be processed is low, and “large dots” aregenerated instead of the “small dots” when the average density of theregion is high so as to express the density of the region, but thegeneration ratio of the “large dots” is greater than that of FIGS. 12Aand 12B. Further, the dot ratio table 300 of FIG. 13C specifies thatdots having three kinds of sizes including “middle dots (Mdot)” having amiddle size in addition to “small dots” and “large dots,” are combinedso as to express the density of the region.

However, since using the dot ratio tables 300 of FIGS. 35A and 35B canuse each dot size effectively like other regions as criteria, a suddenimage quality change is not caused, but a natural image is obtained.

Incidentally, FIG. 13C shows an example of the dot ratio tables 300 forthe nozzles which cause flight deflection and tend to increase in dotsize, similarly to FIGS. 35A and 35B, and is designed with the idea thatthe shape of the dot ratio tables 300 does not change (although each dotsize is generated, the generation frequency becomes less in eachdensity).

Design can be controlled so that these dot ratio tables 300 may be setaccording to the density (ink discharge amount) and the flightdeflection amount of nozzles, and banding avoiding may be realized onlyby selection of a dot ratio table 300.

Further, in above first and second embodiments, the selection of a dotratio table is made from the three kinds of dot ratio tables 300according to the flight deflection amount (corresponding to the size ofthe density unevenness). Specifically, “Table 1” is selected when theflight deflection amount is smaller than a first threshold, “Table 3” isselected when the flight deflection amount is greater than a secondthreshold, and “Table 2” is selected when the flight deflection amountis located between the first threshold and the second threshold.However, the invention is not limited thereto, and it may be possible touse combinations of any two kinds of dot ratio tables (for example,Table 1 and Table 2) according to the size of the flight deflectionamount or the density fluctuation amount (the size of the densityunevenness) among the three kinds of tables.

Hereinafter, a method of using combinations of two kinds of dot ratiotables will be described specifically with reference to FIG. 36. Here,FIG. 36 is a view showing the relationship between the flight deflectionamount (the density fluctuation amount), and the use ratio of the dotratio tables 1 to 3 shown in FIGS. 12A to 12C.

Referring to FIGS. 12A to 12C, the generation ratios of S dot and L dotof Table 1 (FIG. 12A) are defined as S1 and L1, respectively, thegeneration ratios of S dot and L dot of Table 2 (FIG. 12B) are definedas S2 and L2, respectively, and the generation ratios of S dot and L dotof Table 3 (FIG. 12C) are defined as S3 and L3, respectively. Here, acase where the generation ratio of S dot and L dot for a target nozzle(processing region) is determined will be described using the table useratio shown in FIG. 36. In addition, the first threshold and secondthreshold in FIG. 36 are the thresholds in FIG. 19.

The density fluctuation amount (the flight deflection amount) of thetarget nozzle (processing region) is defined as P1 shown in FIG. 36. Asshown in FIG. 36, P1 is a value obtained by combining two kinds oftables, i.e., Table 1 and Table 2. Hereinafter, description will be madeassuming that the use ratio of Table 1 and Table 2 is 7:3. In this case,as shown in the following Expression (1), the sum of the result obtainedby multiplying the generation ratio of S dot of Table 1 by 0.7 in theamount P1 of density fluctuation (the flight deflection amount) and theresult obtained by multiplying the generation ratio of S dot of Table 2by 0.3 becomes the generation ratio of S dot when Table 1 and Table 2are combined. Similarly, as shown in the following Expression (2), thesum of the result obtained by multiplying the generation ratio of L dotof Table 1 by 0.7 in the amount P1 of density fluctuation (the flightdeflection amount) and the result obtained by multiplying the generationratio of L dot of Table 2 by 0.3 becomes the generation ratio of L dotwhen Table 1 and Table 2 are combined.Generation ratio of S dot when Tables 1 and 2 arecombined=0.7S1+0.3S2  (1)Generation ratio of L dot when Tables 1 and 2 arecombined=0.7L1+0.3L2  (2)

Similarly, a case in which the density fluctuation amount (the flightdeflection amount) of the target nozzle (processing region) is P2 shownin FIG. 36 will be described. As shown in FIG. 36, P2 is a valueobtained by combining two kinds of tables, i.e., Table 2 and Table 3.Hereinafter, a description will be made assuming that the use ratio ofTable 2 and Table 3 is 4:6. In this case, as shown in the followingExpression (3), the sum of the result obtained by multiplying thegeneration ratio of S dot of Table 2 by 0.4 in the amount P2 of densityfluctuation (the flight deflection amount) and the result obtained bymultiplying the generation ratio of S dot of Table 2 by 0.6 becomes thegeneration ratio of S dot when Table 2 and Table 3 are combined.Similarly, as shown in the following Expression (4), the sum of theresult obtained by multiplying the generation ratio of L dot of Table 1by 0.4 in the amount P2 of density fluctuation (the flight deflectionamount) and the result obtained by multiplying the generation ratio of Ldot of Table 3 by 0.6 becomes the generation ratio of L dot when Table 2and Table 3 are combined.Generation ratio of S dot when Tables 2 and 3 arecombined=0.4S2+0.6S3  (3)Generation ratio of L dot when Tables 2 and 3 arecombined=0.4L2+0.6L3  (4)

As described above, in a case in which the density fluctuation amount(the flight deflection amount) of a target nozzle (processing region) isa value that is smaller than the first threshold and approximate to thefirst threshold like P1 shown in FIG. 36, N-valued data can be generatedin a more suitable dot generation ratio by using a combination of Table1 and Table 2 according to a predetermined ratio without using onlyTable 1 as in the above first and second embodiments. This is similarlyapplied to P2 of FIG. 36. Since this enables dots to be formed in a moresuitable mixing ratio, the density unevenness can be eliminated moreeffectively.

Further, in a case in which the density fluctuation amount (the flightdeflection amount) of a target nozzle (processing region) is P0 and P3shown in FIG. 36, the generation ratio of S dot is determined by usingonly Table 1 because P0 is a value that is smaller than the firstthreshold and away from the first threshold, and the generation ratio ofL dot is determined by using only Table 3 because P3 is a value that isgreater than the second threshold, and away from the second threshold.

1. A printing apparatus comprising: a print head in which a plurality ofnozzles which can print different sizes of dots are arranged; an imagedata acquiring unit which acquires image data having M-value densityinformation (M≧3) for every pixel; a density unevenness informationacquiring unit which acquires information on density unevenness of thenozzles of the print head; an N-valued data generating unit whichperforms N-valued processing (M>N≧2) on the image data acquired by theimage data acquiring unit to generate N-valued data; a print datagenerating unit which generates print data from the N-valued datagenerated by the N-valued data generating unit; and a printing unitwhich performs printing using the print head based on the print datagenerated by the print data generating unit, wherein the N-valued datagenerating unit determines generation ratios of the different sizes ofdots for every predetermined region of the image data acquired by theimage data acquiring unit based on the density unevenness informationacquired by the density unevenness information acquiring unit, andperforms N-valued processing (M>N≧2) on the image data based on thedetermined generation ratios.
 2. The printing apparatus according toclaim 1, wherein the information on the density unevenness includesinformation on a difference value between a density value of a dotformed by each of the nozzles of the print head and an assumed densityvalue.
 3. The printing apparatus according to claim 2, wherein if it isdetermined that the difference value of the density value of the dot tobe formed by each of the nozzles of the print head is greater than apredetermined threshold based on the information on the densityunevenness, the N-valued data generating unit makes the density valuegreater than a density value that is generated when the generation ratioof large-sized dots is not determined.
 4. The printing apparatusaccording to claim 3, further comprising: a density unevennesscorrecting unit which corrects the density value of each pixel of theimage data acquired by the image data acquiring unit based on thedensity unevenness information acquired by the density unevennessinformation acquiring unit, wherein the N-valued data generating unitperforms N-valued processing on the image data corrected by the densityunevenness correcting unit to generate N-valued data.
 5. The printingapparatus according to claim 4, wherein the dot ratio informationselecting unit selects a predetermined item of dot ratio informationfrom the dot ratio information stored in the dot ratio informationstoring unit for every plural nozzles including a target nozzle of theprint head, and nozzles proximate the target nozzle.
 6. The printingapparatus according to claim 4, wherein the dot ratio informationselecting unit selects a predetermined item of dot ratio informationamong the dot ratio information stored in the dot ratio informationstoring unit based on the information on a print head printing positiondeviation amount among the density unevenness information acquired bythe density unevenness information acquiring unit.
 7. The printingapparatus according to claim 4, wherein the dot ratio informationselecting unit is adapted to select two or more kinds of dot ratioinformation among the dot ratio information stored in the dot ratioinformation storing unit based on the information on a printing positiondeviation amount of the print head among the density unevennessinformation acquired by the density unevenness information acquiringunit, and wherein the N-valued data generating unit determines thegeneration ratios of the different sizes of dots for every predeterminedregion of the image data based on the two or more kinds of dot ratioinformation selected by the dot ratio information selecting unit, andperforms N-valued processing (M>N≧2) on the image data based on thedetermined generation ratios.
 8. The printing apparatus according toclaim 3, further comprising: a dot ratio information storing unit whichstores dot ratio information which specifies mixing ratios of thedifferent sizes of dots, and a dot ratio information selecting unitwhich selects a predetermined item of dot ratio information among thedot ratio information stored in the dot ratio information storing unitbased on the density unevenness information acquired by the densityunevenness information acquiring unit, wherein the N-valued datagenerating unit determines the generation ratios of the different sizesof dots for every predetermined region of the image data acquired by theimage data acquiring unit based on the dot ratio information selected bythe dot ratio information selecting unit, and performs N-valuedprocessing (M>N≧2) on the image data based on the determined generationratios.
 9. The printing apparatus according to claim 3, furthercomprising: a density unevenness correcting unit which corrects thedensity value of each pixel of the image data acquired by the image dataacquiring unit based on the density unevenness information acquired bythe density unevenness information acquiring unit, a dot ratioinformation storing unit which stores dot ratio information whichspecifies mixing ratios of the different sizes of dots, and a dot ratioinformation selecting unit which selects a predetermined item of dotratio information among the dot ratio information stored in the dotratio information storing unit based on the density unevennessinformation acquired by the density unevenness information acquiringunit, wherein the N-valued data generating unit determines thegeneration ratios of the different sizes of dots for every predeterminedregion of the image data corrected by the density unevenness correctingunit based on the dot ratio information selected by the dot ratioinformation selecting unit, and performs N-valued processing (M>N≧2) onthe image data based on the determined generation ratios.
 10. A printingprogram stored on a computer readable medium for causing a computer tofunction as: an image data acquiring unit which acquires image datahaving M-value density information (M≧3) for every pixel; a densityunevenness information acquiring unit which acquires information ondensity unevenness of the nozzles of a print head which can printdifferent sizes of dots; an N-valued data generating unit which performsN-valued processing (M>N≧2) on the image data acquired by the image dataacquiring unit to generate N-valued data; a print data generating unitwhich generates print data from the N-valued data generated by theN-valued data generating unit; and a printing unit which performsprinting based on the print data generated by the print data generatingunit, wherein the program causes the N-valued data generating unit todetermine generation ratios of the different sizes of dots for everypredetermined region of the image data acquired by the image dataacquiring unit based on the density unevenness information acquired bythe density unevenness information acquiring unit, and to performN-valued processing (M>N≧2) on the image data based on the determinedgeneration ratios.
 11. A printing method comprising: acquiring imagedata having M-value density information (M≧3) for every pixel; acquiringinformation on density unevenness of nozzles of a print head which canprint different sizes of dots; performing N-valued processing (M>N≧2) onthe image data acquired in the step of acquiring the image data togenerate N-valued data; generating print data from the N-valued datagenerated in the step of generating the N-valued data; and performingprinting using the print head based on the print data generated in thestep of generating the print data, wherein, in the step of generatingthe N-valued data, generation ratios of the different sizes of dots aredetermined for every predetermined region of the image data acquired inthe step of generating the image data based on the density unevennessinformation acquired in the step of acquiring the density unevennessinformation, and N-value processing (M>N≧2) is performed on the imagedata based on the determined generation ratios.
 12. An image processingapparatus comprising: an image data acquiring unit which acquires imagedata having M-value density information (M≧3) for every pixel; a densityunevenness information acquiring unit which acquires information ondensity unevenness of nozzles of a print head which can print differentsizes of dots; an N-valued data generating unit which performs N-valuedprocessing (M>N≧2) on the image data acquired by the image dataacquiring unit to generate N-valued data; a print data generating unitwhich generates print data from the N-valued data generated by theN-valued data generating unit; and a printing unit which performsprinting based on the print data generated by the print data generatingunit, wherein the N-valued data generating unit determines generationratios of the different sizes of dots for every predetermined region ofthe image data acquired by the image data acquiring unit based on thedensity unevenness information acquired by the density unevennessinformation acquiring unit, and performs N-valued processing (M>N≧2) onthe image data based on the determined generation ratios.
 13. An imageprocessing program stored on a computer readable medium for causing acomputer to function as: an image data acquiring unit which acquiresimage data having M-value density information (M≧3) for every pixel; adensity unevenness information acquiring unit which acquires informationon density unevenness of nozzles of a print head which can printdifferent sizes of dots; an N-valued data generating unit which performsN-valued processing (M>N≧2) on the image data acquired by the image dataacquiring unit to generate N-valued data; and a print data generatingunit which generates print data from the N-valued data generated by theN-valued data generating unit, wherein the program causes the N-valueddata generating unit to determine generation ratios of the differentsizes of dots for every predetermined region of the image data acquiredby the image data acquiring unit based on the density unevennessinformation acquired by the density unevenness information acquiringunit, and to perform N-valued processing (M>N≧2) on the image data basedon the determined generation ratios.
 14. An image processing methodcomprising: acquiring image data having M-value density information(M≧3) for every pixel; acquiring information on density unevenness ofnozzles which can print different sizes of dots; performing N-valuedprocessing (M>N≧2) on the image data acquired in the step of acquiringthe image data to generate N-valued data; and generating print data fromthe N-valued data generated in the step of generating the N-valued data,wherein, in the step of generating the N-valued data, generation ratiosof the different sizes of dots are determined for every predeterminedregion of the image data acquired in the step of generating the imagedata based on the density unevenness information acquired in the step ofacquiring the density unevenness information, and N-value processing(M>N≧2) is performed on the image data based on the determinedgeneration ratios.